Blown Film Workbook Draft

Higher Institute for Plastics Fabrication

WORKBOOK for

Blown Film Extrusion Practical Course

Prepared by

Blown Film Extrusion Department 1st Edition 2009

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Wo r k b o o k f o r B l o w n F i l m P r a c t i c a l C o u r s e

ACKNOWLEDGEMENT

In its program to continuously improve the quality of instructions at the Higher Institute for Plastics Fabrication, the Curriculum Steering Committee initiated the creation of the workbooks for all practical courses being offered in the Institute. The Committee is headed by Dr. Khaled Al-Ghefaili, and the members are Dr. Ahmad Al-Ghamdi, Mr. Hiroshi Takeshita, Engr. Issa AlKhormi, Mr. Sumio Iwase, Mr. Kazuhiko Sawada, Mr. Sanjay Rawat, Mr. Zakaria Musa, and Mr. Virgilio Calpe.

This is the HIPF Workbook for Injection Molding for Practical Course. The contents of this workbook were compiled through the efforts of the members of the Blown Film Department, namely, Raul R. Clave (Head of the Department), Isagani Aldover, Philip Floyd Yumul, Jovanny Quilala, Jovef Pangue, Alfred Bacosa, Kirankumar Daraji (Senior Instructors) and Mr. Sumio Iwase and Mr. Takuma Nakashima (Blown Film Expert Advisers). Editing, formatting and design by Virgilio Calpe.

February 2009

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ACKNOWLEDGEMENT

In its program to continuously improve the quality of instructions at the Higher Institute for Plastics Fabrication, the Curriculum Steering Committee initiated the creation of the workbooks for all practical courses being offered in the Institute. The Committee is headed by Dr. Khaled Al-Ghefaili, and the members are Dr. Ahmad Al-Ghamdi, Mr. Hiroshi Takeshita, Engr. Issa AlKhormi, Mr. Sumio Iwase, Mr. Kazuhiko Sawada, Mr. Sanjay Rawat, Mr. Zakaria Musa, and Mr. Virgilio Calpe.

This is the HIPF Workbook for Injection Molding for Practical Course. The contents of this workbook were compiled through the efforts of the members of the Blown Film Department, namely, Raul R. Clave (Head of the Department), Isagani Aldover, Philip Floyd Yumul, Jovanny Quilala, Jovef Pangue, Alfred Bacosa, Kirankumar Daraji (Senior Instructors) and Mr. Sumio Iwase and Mr. Takuma Nakashima (Blown Film Expert Advisers). Editing, formatting and design by Virgilio Calpe.

February 2009

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TABLE OF CONTENTS Introduction … … … … … … … … … … … … … … … … … … .

4

Course Objectives … … … … … … … … … … … … … … … … .

5

General Safety Guidelines … … … … … … … … … … … … … ...

6

Grades Summary Sheet … … … … … … … … … … … … … … ...

7

Workshop Activities Activity 1—Basic Theory of Blown Film Extrusion … … … … … ..

8

Activity 2—Polyethylene Films… … … … … … … … … … … …

14

Activity 3—Emergency Stop and Safety Devices … … … … … … .

19

Activity 4—Blown Film Die … … … … … … … … … … … … …

26

Activity 5—Blown Film Air Cooling Ring … … … … … … … … ..

31

Activity 6—Blown Film Width and Thickness… … … … … … … ..

37

Activity 7—Corona Treatment … … … … … … … … … … … … .

42

Activity 8—Flexographic Printing … … … … … … … … … … …

48

Activity 9—Bag Making … … … … … … … … … … … … … … .

55

Activity 10—Polyethylene Film Recycling … … … … … … … … .

64

Activity 11—Practice Plant Operations (LDPE) … …. … … … … ..

73

Activity 12—Practice Plant Operations (LLDPE) … …. … … … … .

81

Activity 13—Practice Plant Operations (HDPE) … …. … … … … ..

85

Formulas … … … … … … … … … … … … … … … … … … …

89

Glossary … … … … … … … … … … … … … … … … … … … .

92

References … … … … … … … … … … … … … … … … … … ...

110 Page 3


INTRODUCTION Blown film extrusion is one of the most commonly used thin-gauge fabrication processes in the world. The majority of the commodity films such as grocery bags, agricultural films and other flexible packaging films used by consumers consumers are produced by this method. The process of producing film by extruding molten molten resin into a continuous tube is simple. Yet, in fact the system is one of the most complex and sensitive of all the plastics fabricating technologies and it presents many inherent difficulties. A simple blown film line consists of an extruder, die, air ring, iris or bubble cage, collapsing frame, and a winder.

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COURSE OBJECTIVES The purpose of this workbook is to enable the trainees to understand and carry out important activities being done in a blown film extrusion process. Focus will be on the most important functions of the machine and the terminologies used in the enterprise.

Upon successful completion of this course, the trainee will be able to: •

Know the main components of film extruders and their purposes.

•

Describe blown film extrusion process.

•

Identify common polyethylene films.

•

Perform emergency stop using emergency switches.

•

Know the operation of an air ring, die, nip rolls and gusseting equipment.

•

Know the operation of a simple flexographic in-line printer.

•

Know the basic operation of a recycling machine.

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GENERAL SAFETY PRECAUTIONS Instead of starting operations carelessly, all trainees should discuss the following before starting any activity: (1.) What types of activities are we going to do? (2.) What kind of risks are hidden behind those types of activities? (3.) What should we do to avoid those risks?

Here are some safety reminders to always keep in mind: •

Keep the work area clean at all times.

•

Use proper hand gloves. Avoid using loose l oose hand gloves.

•

• •

• •

•

•

Use the appropriate tool and wear protective dry gloves when you throw away purged resin. Do not lean against the cage guard of the ladder when you work. Pay attention to where your hands are to ensure that your hands are not pinched between rollers and other rotating equipment. Do not run the machine without the protective covers on rotating parts. Avoid clothing or accessories that could easily be pinched or caught in machines. Specifically, do not wear items that hang far from your neck such as long necklaces and IDs’. Do not wear rings or loose bracelets. Do not not wear clothing that is pleated, sags or or has strings. Make sure that you button or fasten your shirt and jacket cuffs, pant cuffs and jacket hem. Do not stand in front of the die.

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GRADES SUMMARY SHEET

Trainee Name: _________________________ Group: ________ Semester ___ School Year ___________

ACTIVITIES

GRADE

Activity 1—Basic Theory of Blown Film Extrusion Activity 2—Polyethylene Films Activity 3—Emergency Stop and Safety Devices Activity 4—Blown Film Die Activity 5—Blown Film Air Cooling Ring Activity 6—Blown Film Width and Thickness Activity 7—Corona Treatment Activity 8—Flexographic Printing Activity 9—Bag Making Activity 10—Polyethylene Film Recycling Activity 11—Practice Plant Operations (LDPE) Activity 12—Practice Plant Operations (LLDPE) Activity 13—Practice Plant Operations (HDPE) AVERAGE GRADE Page 7


WORKSHOP ACTIVITY #1

Basic Theory of Blown Film Extrusion THEORETICAL BACKGROUND Blown films are created by feeding plastics pellets into an extruder where they are melted and homogenised before they are pumped through a circular blown film die. The melted plastics form a continuous tube which is drawn from the die. It is inflated and simultaneously cooled by rapidly moving air . The tube, also called a “bubble,” is then flattened as it passes the collapsing frames and drawn through nip rolls and over idler rolls to a winder which pulls and winds the finished rolls of film. A typical film blown film machine consists of the following five major units: •

Extruder unit— converts the solid pellets into hot melt.

•

Die unit— forms the hot melt into tube.

•

Cooling unit— cools down and solidifies the hot melt.

•

Take-off unit— pulls and flattens the tube at constant speed.

•

Winding unit— winds-up the flattened tube into finish rolls.

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Wo r k b o o k f o r B l o w n F i l m P r a c t i c a l C o u r s e WORKSHOP ACTIVITY #1—Basic Theory of Blown Film Extrusion

OBJECTIVES OF THE ACTIVITY 1. To learn the basics of operating a blown film machine 2. To identify the parts of the five major units of a blown film and their elements

PROCEDURE PART I—The Basic Operations of Blown Film Machine 1. Go to the Workshop floor and observe any of the blown film machine that is being run by your Instructor. 2. Using data sheet on the following pages, list down accordingly the steps of the blown film process you have observed. Example: Step 1. Put material in the hopper. Step 2. etc… PART II—The Five Major Units of a Blown Film Machine 1. Using the drawing of Blown Film Machine in your data sheet, label the following: a. name of the part/s of each major units. b. name the other elements needed in the process.

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 C u t R e p o r t F o r m a n d S u b m i t t o I n s t r u c t o r

Report Form - Page 1 of 4

D ATA S H E E T ACTIVITY #1—Basic Theory of Blown Film Extrusi on TRAINEE NAME

GROUP NO.

PART I—The Basic Operations of Blown Film Machine Steps in Blown Film Operations Step No. Description of the Step

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D ATA S H E E T ACTIVITY #1—Basic Theory of Blown Film Extrusi on TRAINEE NAME

GROUP NO.

PART II—The Five Major Units of a Blown Film Machine

m a r g a i D s s e c o r P m l i F n w o l B e h t l e b a l y l r e p o r P Page 11




QUESTIONS & EXERCISES A. Choose the correct answer. 1.

What is the most common material used for blown films? (a.) PVC (c.) Nylon (b.) PET (d.) PE

2.

What is the common type of blown film used all over the world? (a.) Downward BF (b.) Horizontal BF

3.

(c.) Upward BF (d.) None of the above

What part of the blown film machine makes the screw rotates? (a.) blower (b.) main motor

4.

(c.) haul-off (d.) winder

What is the process of feeding a single die with two or more different polymer melt streams? (a.) blower (b.) main motor

(c.) haul-off (d.) none of the above

B. How does blown film differs from other plastics fabrications? Check () if applicable, and cross out ( ) if not applicable.

PROCESS

Die

Mould

Screw and

Haul-off /

Barrel

Take-off

Winder

Blown Film Extrusion Blow Molding Pipe Extrusion Injection Molding

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CONCLUSION & RECOMMENDATIONS

___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________

________________________ DATE: __________________

TRAINEE’S SIGNATURE

INSTRUCTOR’S COMMENTS

TRAINEE’S GRADE FOR THIS ACTIVITY

________________________ DATE: __________________

INSTRUCTOR’S SIGNATURE Page 13



Polyethylene Films THEORETICAL BACKGROUND

•

•

The ethylene polymer is available in three main grades, low, medium and high density film. Polyethylene, PE, film is slightly opaque, the opacity increasing with density.

•

PE film is waxy to the touch, and is a good moisture barrier.

•

Low and medium density PE films are flexible even when cold.

•

PE is readily heat sealed.

•

•

High density PE film is suitable for boil-in-the-bag packs, whereas low and medium density films are not. PE film that has a lower MFR means a higher molecular weight and better mechanical strength.

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Wo r k b o o k f o r B l o w n F i l m P r a c t i c a l C o u r s e WORKSHOP ACTIVITY #2—Polyethylene Films

OBJECTIVES OF THE ACTIVITY 1. To learn the physical properties of Polyethylene (PE) films 2. To compare the differences among the three common types of PE films used in blown film packaging

PROCEDURE PART I—Physical Characteristics of PE Films 1. Collect three samples for each type of the PE films from the plant •

LDPE @ 400mm & 30microns

•

LLDPE @ 400mm & 30microns

•

HDPE @ 400mm & 30microns

2. Correctly label the different films. 3. Each film sample should have the same thickness, length and width. 4. Try to stretch each film and write your observation in your data sheet.

PART II—Process Parameters for PE Films 1. Try to find the Melt Temperature and Pressure for processing each type of PE films. 2. Write your data in the table provided in your data sheet. 3. Compare MFR, Density, Melt Temperature, and Pressure for each type of PE films. 4. Which materials do you think is the easiest to process?

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D ATA S H E E T ACTIVITY #2—Polyethylene Films TRAINEE NAME

GROUP NO.

PART I—Physical Characteristics of PE Films

Stretch the plastics samples: PE Sample

Observations

LDPE (400mm, 30microns) LLDPE (400mm, 30microns) HDPE (400mm, 30microns)

PART II—Process Parameters for PE Films PE Sample

MFR

Density

LDPE

0.2 to 5

0.912 to 0.925

LLDPE

0.5 to 2

0.912 to 0.925

HDPE

Extruder Melt Temperature

Extruder Melt Pressure

0.03 to 0.1 0.945 to 0.955

Based on the above data, which materials is easy to process?

Why?

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QUESTIONS & EXERCISES Choose the correct answer and mark (



) the correct ones.

1. Which of these films has a better clarity? a. LDPE b. LLDPE c. HDPE 2. Which is the toughest among these polyethylene films? a. HDPE b. LDPE c. LLDPE 3. Which blown film bag is suitable for carrying more weight? a. LLDPE b. LDPE c. HDPE 4. Choose the correct application of LDPE film. a. food packaging b. shopping bag c. garments packaging d. floor covering 5. Which of these films can be stretch more? a. HDPE b. LDPE c. LLDPE

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___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________

________________________ DATE: __________________




________________________ DATE: __________________




Emergency Stop and Safety Devices THEORETICAL BACKGROUND MACHINE SAFETY GUARDS & DEVICES

Safety devices in facilities, machinery and equipment are an essential means of ensuring worker safety. Foolproof devices, failsafe devices and others are used to ensure intrinsic (essential) safety. These devices are usually built into facilities, machinery and equipment so that workers cannot easily remove them.

The foolproof function is a safety mechanism designed with a focus on human factors. On the other hand, the failsafe function is a safety mechanism designed with a focus on the protection of facilities, machinery and equipment.

Types of safety devices typically used in blown film machine: •

Mechanical Interlock

•

Electrical Interlock

All Dangerous spots of the blown film line must be secured by suitable protective devices. If proper guards cannot be mounted due to the conditions at hand, these areas are secured by Emergency devices.

Guarding and Barriers The purpose of machine guarding and barrier is to protect the machine operator and other employees in the work area from hazards created by moving parts, rotating parts, flying chips & sparks. Some examples of this are barrier guards, safety gates, etc.

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Wo r k b o o k f o r B l o w n F i l m P r a c t i c a l C o u r s e WORKSHOP ACTIVITY #3—Emergency Stop and Safety Devices

THEORETICAL BACKGROUND … continued WARNING SIGN

WARNING SIGN

SAFETY COVER

GUARD RAILS

EMERGENCY STOP

EMERGENCY STOP Push

Pull-Down

SAFETY SWITCH

SAFETY GATE Safety Interlock Switch

Electrical Interlock

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OBJECTIVES OF THE ACTIVITY 1. To know the purposes of each of the safety devices installed in a blown film machine 2. To learn how to pause or stop the blown film machine in emergency cases 3. To develop awareness of the dangers of blown film machine if safety devices are tampered or by-passed

PROCEDURE Types of Safety Devices Typically Used in Blown Film Machines Walk around the blown film machine assigned to you by your Instructor and try to locate all the safety devices and the emergency stop buttons.

PART I—Safety Devices and their Functions 1. In your data sheet, write down the names of the safety devices and their functions and answer the questions.

PART II—Emergency Stops 1. In your data sheet, indicate all the emergency stop buttons of the blown film machine available in WS02 and answer all the questions.

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D ATA S H E E T ACTIVITY #3—Emergency Stop and Safety Devices TRAINEE NAME

GROUP NO.

PART I—Safety Devices and their Functions Safety Devices of Blown Film Machine, where are they?

SAFETY DEVICES of BLOWN FILM MACHINE 1. 2. 3. 4. 5.

1. Do these safety devices really help by reminding you of the danger if YES NO they are not activated? 2. How?

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D ATA S H E E T ACTIVITY #3—Emergency Stop and Safety Devices TRAINEE NAME

GROUP NO.

PART II—Emergency Stops Emergency stop buttons of Blown Film Machine, where are they?

1. When are we going to use the emergency stop buttons, is it during scheduled shutdown? YES

NO

2. Why?

3. If something happens to the machine or to the operator and we need to stop immediately, are we going to use the emergency stop? YES

NO

4. Why?

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QUESTIONS & EXERCISES Choose the correct answer. 1. What type of emergency device is installed above and across the width of the winding station? (a.) emergency stop button

(c.) emergency stop cord

(b.) warning alarm

(d.) none of the above

2. What warning sign is available in the machine indicating danger of being burn? (a.)

(b.)

(c.)

(d.)

3. What will you do to stop the machine in case of emergency? (a.) switch off the main switch (b.) leave the machine (c.) press the “Emergency Stop” push button (d.) follow the shutdown procedure 4. Which mandatory safety sign that informs operator to wear hand protection? (a.)

(b.)

(c.)

(d.)

5. Which of the following is an example of safeguarding devices? (a.) printing gear cover (b.) railings (b.) winder gates (c.) all of the above

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___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________

________________________ DATE: __________________




________________________ DATE: __________________




Blown Film Die THEORETICAL BACKGROUND In various kinds of plastics fabrication processes, molten resin that leaves the extruder is forced through an orifice (opening, slit) called a die. By this die the molten resin is given its final shape appropriate for the end product. A die used for blown film extrusion has an annular (ring-shaped) outlet (called a lip) through which the molten resin passes. Such a die is called a circular die. The size of a die is expressed by the lip diameter. The lip diameter ranges from a small diameter of about 30 mm to a large diameter of about 1,500 mm.

The Two Types of Die Lip Gap Adjustments: Figure 4.1 Upper Die Tightening the bolt

A

Upper Die Goes that way

Upper Die Tightening the bolt Upper Die Goes that way

B

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Wo r k b o o k f o r B l o w n F i l m P r a c t i c a l C o u r s e WORKSHOP ACTIVITY #4—Blown Film Die

OBJECTIVES OF THE ACTIVITY 1. To learn the basic principles of die mechanisms 2. To understand the die mechanisms and how to adjust the lip gap

PROCEDURE Important! Before you adjust the gap, you should know which type of adjustable die ring is used for the die available. You should also understand that the adjustable die ring just moves horizontally as a whole by rotating the adjusting bolt.

PART I—Die Lip Adjustment 1. Prepare the half die head available in the Workshop. 2. Examine carefully what type of die lip gap adjustment the die has. 3. Confirm the movement of the die lip. Confirm whether it is A- or B-type lip gap adjustment. 4. When making adjustment, loosen the bolt on the other side first. Refer to Figure 4.1: •

For A type, tightening the bolt will widen the gap.

For this type, when the die ring is screwed in, the ring is moved in a way that pulls the ring with the bolt to widen the lip gap (see Figure 4.1). •

For B type, tightening the bolt will narrow the gap.

For this other type, when the die ring is screwed in, the ring is moved in a way that pushes the ring with the bolt to narrow the lip gap (see Figure 4.1). 5. Try turning the bolts of your die and observe the outer lip movement of the die. Answer all the questions in your data sheet. PART II—Parts of the Die 1. Properly label the parts of the die using the drawing found in your data sheet.

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D ATA S H E E T ACTIVITY #4—Blown Film Die TRAINEE NAME

GROUP NO.

PART I—Die Lip Adjustment 1. Referring to the Figure 4.1, what type of die do we have in Workshop 02 Blown Film? A-Type B-Type 2. What happens when you tighten the bolt of this type?

3. In your own opinion, if you widen the die lip gap, does this makes the corresponding blown film wall thicker? YES NO 4. Why?

PART II—Parts of the Die

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QUESTIONS & EXERCISES 1. It is the part of the Blown Film machine where the molten resin is forced through its round opening slit and forms a tube. a.

screw and barrel

b. adapter c.

die

d. none of these

2. Describe briefly how the material flows as it enters the spiral and outside the spiral. _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________

4. When the die is not properly centered, why is a thinner film produced from the wider die gap and a thicker film from the narrower gap? _______________________________________________________________ _______________________________________________________________ _______________________________________________________________

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___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________

________________________ DATE: __________________




________________________ DATE: __________________




Blown Film Air Cooling Ring THEORETICAL BACKGROUND Blown film air rings are used primarily to stabilize the bubble and secondarily to cool the melt. In plastics forming, a circular manifold distributes an even flow of cool air into a hollow tubular form passing through the manifold. An air ring is installed just above the die in an upward air cooling blown film machine. The air outlet called a lip (or slit) has an annular shape that surrounds the molten resin extruded from the die. Air is introduced into the ring by the blower, and the air is turned into a uniform flow inside the air ring. Then the air is blown through the lip against the molten resin for cooling. If the flow of air blown out of the lip is not uniform, it leads to nonuniform cooling. As a result, film thickness will be uneven. To prevent this, the air ring is designed to ensure uniform air flow over the entire lip. As the molten resin is cooled, it becomes “frosty,” or less clear (transparent), and a solidification border appears. This borderline is called a frost line.

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Wo r k b o o k f o r B l o w n F i l m P r a c t i c a l C o u r s e WORKSHOP ACTIVITY #5—Blown Film Air Cooling Ring

G N I R R I A M L I F N W O L B P I L E L G N I S A F O S T R A P

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OBJECTIVES OF THE ACTIVITY 1. To know the importance of air ring to blown film extrusion 2. To understand the construction of an air ring and how to adjust it

PROCEDURE 1. Run the blown film line assigned to you by your Instructor. 2. With the supervision of your Instructor, set the parameters to produce a 30microns by 300mm lay flat width film. 3. Once the process has stabilized (as checked by your Instructor), adjust the threaded adjusting ring of the air ring by the doing the following trials: •

Trial 1—Turn the adjusting ring one-fourth ( ¼ ) down

•

Trial 2—Turn the adjusting ring another one-fourth ( ¼ ) down

•

Trial 3—Turn the adjusting ring still another one-fourth ( ¼ ) down

•

Trial 4—Turn the adjusting ring one-fourth ( ¼ ) upward

•

Trial 5—Turn the adjusting ring another one-fourth ( ¼ ) upward

4. Allow 5minutes intervals for each trial and ensure that the bubble is stable each time. 5. For each trial, observe what will happen to the bubble and take note of what happens to the height of the frost line. 6. Write all your observations on the table provided in your data sheet, and answer all the questions.

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D ATA S H E E T ACTIVITY #5—Blown Film Air Cooling Ring TRAINEE NAME

GROUP NO.

OBSERVATIONS Trial

Number of Turns

Pressure

No.

and Direction

Reading

1

¼ turn down

2

another ¼ turn down

3

another ¼ turn down

4

¼ turn upward

5

another ¼ turn upward

Bubble Observations

1. When the threaded adjustable ring is adjusted downwards, what happens to the frost line height? goes up or down? goes up

goes down

2. What type of air ring does workshop 02 blown film has, Is it single lip or dual lip? single lip

dual lip

3. How did you know that it is a _____________lip?

4. If the inside of the air ring is dirty and causing obstruction, will you have an even flow of air in the bubble, yes or no? yes

no

5. Does this obstruction cause uneven thickness of the film, yes or no? yes

no

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QUESTIONS & EXERCISES 1. _______________________is the part of the Blown Film machine that uniformly cools and then evenly solidifies (make solid) the molten resin extruded from the die. 2. The blowing angle should be appropriately set depending on the type of resin is used, the type of product being made, and other factors. True or False? 3. In the given drawing below, the air ring is called a dual lip because it has _______________, _________________, and ____________________.

4. In the given drawing below, which of these two air rings is used for LLDPE and which is for HDPE? _________ is for LDPE

_________ is for HDPE

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___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________

________________________ DATE: __________________




________________________ DATE: __________________




Blown Film Width and Thickness THEORETICAL BACKGROUND The width (lay-flat width) and thickness of the film to be made are always specified in blown film extrusion. The operators need to set the width and thickness to the specified values correctly and maintain them within the target level during the processing. Once the process is started, first adjust the lay-flat width to the specified value. The screw rotation speed shall be set to the predetermined speed and the amount of air to be introduced into the bubble shall be adjusted. Then the film thickness shall be next step.

In blown film extrusion, there are various kinds of operation requirements that directly influence on the shape of the bubble. Examples of these requirements are extruder take-off speed and the amount of air that enters the bubble. In particular, they affect the bubble size and vary the film thickness and lay-flat width.

W

t

t = thickness of film W= width of film

D

Rolled Film

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Wo r k b o o k f o r B l o w n F i l m P r a c t i c a l C o u r s e WORKSHOP ACTIVITY #6—Blown Film Width and Thickness

OBJECTIVES OF THE ACTIVITY 1. To learn how to adjust the width and thickness of a blown film bubble

PROCEDURE 1. Run the blown film line assigned to you by your Instructor. 2. With the supervision of your Instructor, set the parameters to produce a 30microns by 300mm lay flat width film. 3. Once the process has stabilized (as checked by your Instructor), record the take-off speed and winder tension on the table in your data sheet under Trial 0. 4. Then do the following trials, each time observing what will happen to the film thickness and film width. Record the new thickness and width on the table in your data sheet. TRIAL No.

ACTION

Trial No.1

Increase the take-off speed by 2m/min. Slightly add tension on winder to adjust the film tension.

Trial No.2

Open the air valve and let air enter the bubble for at least 2 minutes. Wait for another 3minutes. Let your instructor stabilize the bubble. Observe what will hap pen to the bubble.

Trial No.3

Increase the take-off speed by 2m/min. Slightly add tension to winder to adjust the film tension. Observe again what will happen to the thickness of the film.

Trial No.4

Open the air valve and let air enter the bubble for at least 2minutes. Wait for another 3minutes. Try to sta bilize the bubble by yourself while the instructor guides you. Observe what will happen to the bubble.

5. Answer all questions relating to each trial.

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D ATA S H E E T ACTIVITY #6—Blown Film Width and Thickness TRAINEE NAME

GROUP NO.

DATA & OBSERVATIONS Trial #

Take-off Speed, Film Thickness, m/min m

0

30 microns

Winder Tension, N

Width, mm

300mm

1 2 3 4

1. When the haul-off speed is increased in Trial No.1, did the thickness also increased, yes or no? yes

no

2. When you add some more compressed air in Trial No.2, did the width of the film increased, yes or no? yes

no

3. What happened to the bubble when you increased again the haul-off speed in Trial No.3?

4. What happened to the width when you add more compressed air in Trial No.4?

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QUESTIONS & EXERCISES A. Choose the correct answer. 1. What happens to the lay-flat width if more air is introduced into the bubble? (a.) no change

(c.) increase

(b.) decrease


2. If the extruder screw speed is increased, what happens to the film average thickness? (a.) no change

(c.) increase

(b.) decrease


3. What happens to the film average thickness if the take-off speed increased? (a.) no change

(c.) increase

(b.) decrease


4. If the extruder screw speed is decreased, what happens to the film average thickness? (a.) no change

(c.) increase

(b.) decrease


5. What happens to the film average thickness if the take-off speed decreased? (a.) no change

(c.) increase

(b.) decrease


B. How do you decrease the width of lay flat tube?

C. How do you increase the thickness of the film?

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___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________

________________________ DATE: __________________




________________________ DATE: __________________




Corona Treatment THEORETICAL BACKGROUND •

•

•

•

•

If a corona discharge is generated in air, ozone (O3) is created from the oxygen (O2) in the air. Ozone is a powerful oxidizing gas. This ozone oxidizes the surface of plastics film to make it easier for the ink to stick to the film. This method of treating a plastics film surface is called corona discharge treatment . The corona discharge treatment equipment is made up of a high frequency generator, an electrode, and a treater roll. The wetting tension of PE film and PP film that have not been surface treated is around 30 to 35 mN/m. The tension appropriate for printing on these kinds of film is said to be normally around 40 to 45 mN/m. So, what is wetting tension? Treated film surface can be checked by measuring the wetting tension of the film surface. The wetting tension is an indication of the wettability of a solid surface. Normally, wetting tension of a film that is not surface treated is around 30 to 35 mN/m compared to a treated film which has 40 to 45mN/m.

Page 42

Wo r k b o o k f o r B l o w n F i l m P r a c t i c a l C o u r s e WORKSHOP ACTIVITY #7—Corona Treatment

Theoretical background … continued

•

This activity will explain how wettability works with the polyethylene film. Below is the schematic drawing of a corona discharge machine (corona treater).

WETTING TENSION MEASUREMENT •

The approximate wetting tension of a film can measured by using wetting ink supplied by Polyrema. The ink is used to write on the surface of the film and the ink value where there is no “run-off” corresponds to the wetting tension of the film.

Page 43


OBJECTIVES OF THE ACTIVITY 1. To know the importance of corona treater in blown film printing 2. To know how corona treater affects the film quality during secondary processes

PROCEDURE 1. Run a blown film line. 2. Produce a 30microns by 300mm lay flat width LLDPE film. Make sure film passes the corona discharge machine. 3. Once the blown film is stabilized and checked by your instructor, get film samples without the corona treatment, and then with corona treatments at different corona treatment settings. 4. Properly label each sample. 5. Check the wettability of each sample using the wetting ink supplied by POLYREMA. 6. Follow the following settings for the trials: TRIAL NO.

CORONA TREATER SETTING

1

0% treater setting (no corona treatment)

2

40% treater setting

3

70% treater setting

4

90% treater setting

7. Your Instructor will demonstrate how the wetting ink is used. Start from the lowest wetting ink value to the highest, and record the trial results in your data sheet for each of the sample. 8. Record whether “run-off” occurs or not when the sample is tested with each wetting ink values. 9. Answer all questions regarding your observations.

Page 44



D ATA S H E E T ACTIVITY #7—Corona Treatment TRAINEE NAME

GROUP NO.

RUN-OFF OBSERVATIONS Did the line “run-off”?

Trial No.

Treater Setting

1

0%

yes

no

yes

no

yes

no

2

40%

yes

no

yes

no

yes

no

3

70%

yes

no

yes

no

yes

no

4

90%

yes

no

yes

no

yes

no

Wetting Ink 42

Wetting Ink 44

Wetting Ink 46

1. What happened to the wetting ink applied on the first film sample? Did the liquid line run-off? What does this broken line shows?

2. For the 2nd sample (Trial #2) how did the wetting ink behave in the film? Did it run-off too? What does this mean?

4. For the 3rd sample (Trial #3), do you think the value of the corona discharge is very good for printing? Why?

4. For the 4th sample (Trial #4), do you think the value of the corona discharge is very good for printing? Why?

5. What about sealing this film from Trial #4, do you think that the seal will be very good?

Page 45




QUESTIONS & EXERCISES

1.

The method of treating film surface is called a. gusseting b. sealing c. corona discharge treatment.

2. What is the normal surface tension for untreated PE films? a. 20-30 mN/mtr b. 30-35 mN/mtr c. 40-45mN/mtr

3. Using the wetting liquid application and marking a line on the film, if the line breaks-off or runs-off this means the film is a. untreated b. treated

4. Write down the three major parts of a corona discharge machine. a. ______________________________ b. ______________________________ c. ______________________________

Page 46





___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________

________________________ DATE: __________________




________________________ DATE: __________________




Flexographic Printing THEORETICAL BACKGROUND Rotary Printing— is a printing technique in which the impressions are carved on a rubber plate and stuck on a cylinder, or carved on the cylinder itself, so that the printing can be done on long continuous rolls of paper, cardboard, plastic, or a large number of other substrate. Often Used Printing Processes for Blown Film: • Flexographic Printing Rotogravure Printing •

FLEXOGRAPHIC PRINTING

Flexographic printing has an advantage over rotogravure in that it can use a wider range of inks, water-based rather than oil-based inks, and is good at printing on a variety of different materials like plastics, foils, acetate films, brown paper, and other materials used in packaging. Typical products printed using flexography includes flexible packaging, including retail and shopping bags, food and hygiene bag, etc. A flexographic print is made by creating a positive mirrored master of the required image as a 3D relief in a rubber or polymer material. Flexographic plates can be created with analog and digital plate-making processes. The image areas are raised above the non-image areas on the rubber or polymer plate. The ink is transferred from the ink roll which is partially immerged in the ink tank. Then it transfers to the anilox roll (or meter roll) whose texture holds a specific amount of ink since it is covered with thousands of small wells or cups that enable it to meter ink to the printing plate in a uniform thickness evenly and quickly.

Page 48

Wo r k b o o k f o r B l o w n F i l m P r a c t i c a l C o u r s e WORKSHOP ACTIVITY #8—Flexographic Printing

Theoretical Background … continued

PARTS OF A FLEXOGRAPHIC PRINTER

Plate

Anilox

Cylinder

Roller

Impression Cylinder

Fountain Roller

Page 49


OBJECTIVES OF THE ACTIVITY 1. To learn the basic operation of a flexographic printing machine for blown film 2. To know the parts and functions of a flexographic printing machine

PROCEDURE 1. Pre-heat a blown film machine that has in-line flexographic printing machine. 2. Prepare a rubber cliché for flexographic film print run and the schematic drawing of a flexographic printing machine. 3. Mount the rubber plate on the plate cylinder. Make sure of the alignment by following the groove etched on the cylinder surface. See the drawing.

4. Move gear 1 (for Roll 1) towards gear 2 (for Roll 2) and mesh their teeth by about 3mm by turning knob C clockwise. 5. Pour ink in the ink pan. Ink level at least a few millimetre of the fountain roller lower portion. 6. Switch-on the printing drive.

Page 50


Procedure … continued

7. Move the fountain roller 3 towards the anilox roller 4 by turning knob A clockwise. Observe the ink between these rollers. Putting more pressure between roller 3 and 4 means reducing the ink on the anilox concave surface and lesser ink will be transferred to the rubber plate. 8. Move carriage of 3 & 4 towards 1 by turning the knob B until ink from the anilox is transferred to the rubber plate. 9. Activate the pneumatic cylinder for the carriage D and observe the printing on the film. 10. If print does not appear yet, turn knob C slower clockwise until print appears. Note: Each of the specific knobs has to be adjusted to attain a good ink tone balance and better quality print. 10. When you feel you have attained the best print, take a sample printed film and cut the printed portion. 11. Attach the printed film in your data sheet.

Page 51



D ATA S H E E T ACTIVITY #8—Flexographic Printing TRAINEE NAME

GROUP NO.

1. When you pressed the fountain roller with the anilox roller, does this mean we are reducing the ink being transferred to the printing plate? YES

NO

2. What is the function of knob A?

3. When you pressed carriage 3 & 4 to roller 1, did the image appear on the film? YES

NO

4. What is the function of knob B?

FLEXOGRAPHIC PRINTED FILM

ATTACH YOUR PRINTED FILM HERE! Page 52




QUESTIONS & EXERCISES Choose correct answer. 1.

Which type of printing is done on polyethylene blown film? a. Screen printing b. Rotogravure printing c. Laser printing d. Flexographic printing

2.

Which process is done before printing the polyethylene film? a. Heat treatment b. Chemical treatment c. Corona treatment d. Laser treatment

3.

Why do plastics surfaces require pre-treatment for printing? a. To make plastic thicker b. To make plastic stronger c. To make plastic more decorative d. To make strong ink bonding on surface

4.

What type of chemical (thinner) is used to make printing ink thin and dryable during flexographic printing? a. Acid b. Kerosene c. Petrol d. Alcohol

5.

What is that rubber-like material we use in flexographic in making a printing plate? a. PVC b. Photopolymer c. Polyethylene d. None of these

Page 53





___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________

________________________ DATE: __________________




________________________ DATE: __________________




Bag Making THEORETICAL BACKGROUND Every day, our lives are touched by plastics packaging products. Polyethylene bag is one of the best applications of packaging products. Polyethylene bag is used for various purposes like shopping, grocery, laundry, food packaging, garments, textiles, agriculture, industrial products packaging, garbage, waste management, etc. There are mainly two types of methods to make polyethylene bags. •

Bottom sealed bag

•

Top and bottom sealed bag

Examples of Bottom Sealed Bag Products

Examples of Top and Bottom Sealed Bag Products

Page 55

Wo r k b o o k f o r B l o w n F i l m P r a c t i c a l C o u r s e WORKSHOP ACTIVITY #9—Bag Making

Theoretical Background … continued BOTTOM SEALING DIAGRAM

BOTTOM SEALING PROCESS FLOW

Page 56


Theoretical Background … continued DOUBLE SEALING DIAGRAM

DOUBLE SEALING PROCESS FLOW

Page 57


Theoretical Background … continued TYPES OF BAGS

EXAMPLES OF BAG MAKING PRODUCTS

Page 58


OBJECTIVES OF THE ACTIVITY 1. 2. 3.

To learn making polyethylene poly bags for various applications To learn the proper adjustment of sealing temperature to come up with acceptable product To determine the effect of product type on the production output rate

PROCEDURE PART I—Sealing Temperature for LDPE and HDPE Bags 1. Familiarize yourself with the bag making machine assigned to you by your Instructor. 2. Determine the effect of changing the sealing temperature to final product by changing the temperature setting. 3. Make 5 trials with 5 different temperatures using LDPE film. 4. Each time you change the temperature, record the bag cutting speed and inspect the product if acceptable or not . 5. Record all your data in your data sheet. 6. Do the same for HDPE film.

PART II—Production Output 1. Run five (5) different bag products (different sizes and materials) at constant speed using the machine assigned to you by your Instructor. 2. For each run, record the bag cutting speed and the production output (bags/min). 3. Record all your data in your data sheet.

Page 59



D ATA S H E E T ACTIVITY #9—Bag Making TRAINEE NAME

GROUP NO.

PART I—Sealing Temperature for LDPE and HDPE Bags SEALING TEMPERATURE FOR LDPE BAGS Trial No.

Sealing Temperature

Bag Cutting Speed

Sealing Quality

1

accepted

rejected

2

accepted

rejected

3

accepted

rejected

4

accepted

rejected

5

accepted

rejected

SEALING TEMPERATURE FOR HDPE BAGS Trial No.

Sealing Temperature

Bag Cutting Speed

Sealing Quality

1

accepted

rejected

2

accepted

rejected

3

accepted

rejected

4

accepted

rejected

5

accepted

rejected

Page 60



D ATA S H E E T ACTIVITY #9—Bag Making TRAINEE NAME

GROUP NO.

PART II—Production Output

Trial No.

Material

Bag Size (length)

Bag Cutting Speed

Product Rate (bags/min)

1

2

3

4

5

Page 61




QUESTIONS & EXERCISES 1. Which of these three are the bottom seal and the top & bottom seal bag? ____________ is the bottom seal bag. ____________ is the top & bottom seal bag.

2. In the given drawing, why did they call this a top and bottom sealing? Explain briefly. ___________________________ ___________________________ ___________________________ ___________________________ ___________________________ ___________________________ ___________________________ ___________________________

3. Give at least two applications of this top & bottom sealed bags. Clue: bags that can be found in a market. Applications:

_______________________________ _______________________________

Page 62





___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________

________________________ DATE: __________________




________________________ DATE: __________________




Polyethylene Film Recycling THEORETICAL BACKGROUND Recycling Procedure for Polyethylene Film 1. Start machine heat-up. Set the temperature according to the required setting for the type of material to be recycled. Scrap Scrap Material

LDPE

LLDPE

HDPE

Temperature Settings ºC

180 - 200

190 - 210

195 - 220

2. Check the cooling water supply in/out and ensure that it is ON. OUT

IN

3. Set the shredder temperature at 60°C initially, then increase up to 100°C, as temperature increases after shredder start. Shredder Temperature

4. Start feeding scraps in shredder drum, ensuring that no metal or foreign matter is present. Set shredder speed to 45rpm maximum. The load must not exceed 22amps.

Speed Control

Page 64

Wo r k b o o k f o r B l o w n F i l m P r a c t i c a l C o u r s e WORKSHOP ACTIVITY #10—Polyethylene Film Recycling

Theoretical Background … continued 5. After reaching to the set barrel temperature, clean the screen or change if required and check breaker plate also.

Screen Change Controls Up/Down

Screen Cleaning

6. Connect conveyor to the shredder and after ensuring metal detector is functioning, put conveyor in auto mode. Also connect the cooling water chamber to die-face cutter and tighten the screw properly.

7. When shedder drum temperature reaches 90°C, and barrel temperature, 185°C to 220°C, start oil pump, water pump, vibrator, blowers, and centrifuge.

Page 65


Theoretical Background … continued 8. Start die face cutter and set speed to 1500 initially. Increase die face cutter speed in order to maintain pellet size of 2mm. Monitor the size of pellets and adjust the speed when needed.

Variable Speed Control

9. Start extruder at 25 rpm initially, then increase gradually up to 45 rpm. Observe the ampere meter to control motor load (max 40 amps).

Extruder Speed

Extruder Amps

Setting

Meter

10. Observe smooth operation.

Page 66


OBJECTIVES OF THE ACTIVITY 1. To learn recycling machine operation

PROCEDURE .Observe the recycling machine start up procedure and write start-up steps in the given work sheet.(worksheet#9.1) Write your observations and fill data in process parameter sheet ( work sheet #9.2)

PART I—Recycling Machine Startup Procedure 1. Observe the startup procedure for the recycling machine as performed by your Instructor. 2. In your data sheet, write down the steps on the table provided.

PART II—Recycling Machine Process Parameters 1. Observe the actual recycling run for different plastics materials. 2. Use the Process Monitoring Sheet provided in your data sheet to record your data on the actual machine run.

Page 67



D ATA S H E E T ACTIVITY #10—Polyethylene Film Recycling TRAINEE NAME

GROUP NO.

PART I—Recycling Machine Startup Procedure START PROCEDURE STEP OBSERVED 1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

Page 68



D ATA S H E E T ACTIVITY #10—Polyethylene Film Recycling TRAINEE NAME

GROUP NO.

PART II—Recycling Machine Process Parameters Process Monitoring Sheet—Recycling Machine SCRAP MATERIALS PROCESS PARAMETERS

LLDPE

LDPE

HDPE

Cylinder 1

Cylinder 2 B a r r e l T e m p e r a t u r e

Cylinder 3

Cylinder 4

Joint

Filter

Die Shredder Temperature Shredder Speed Shredder Motor Load (Amps) Extruder Speed Extruder Motor Load (Amps) Cutting Speed

Page 69




QUESTIONS & EXERCISES Choose correct answer. 1. What are the advantages of recycling plastics? a. By recycling we can make more plastics b. Making plastics cheaper c. Recycling machinery business can grow up d. Reduce the consumption of energy and less pollution 2. What is the “STANDARD MARKING CODE” for HDPE? a.

b.

c.

d.

3. Why are “STANDARD MARKING CODES” developed? a. To identify the strength of each plastics b. To identify the cost of each plastics c. To understand the number of times the plastics can be recycled d. To help consumers identify and sort the main types of plastic 4. What is the consumption of plastics in packaging industries? a. 35%

b. 25%

c. 30%

d. 15%

5. What is the importance of oil circulation in the gear box of the extruder? a. To provide lubrication and reduce friction b. To increase the speed of an extruder c. To save power consumption of machine d. For cooling the gear box 6. Select the barrel temperature (ºC ) range for HDPE scrap material a. 195, 200, 205, 210, 215, 220, 225 b. 165, 170, 175, 180, 185, 190, 195 c. 175, 180, 185, 190, 195, 200, 205 d. 170, 180, 180, 187, 190, 190, 195 7. Why is a metal detector provided on the conveyor? a. To sense metal and allow it to go into the shredder and extruder b. To sense metal and save the extruder from damage c. To measure the weight of plastics fed into the shredder d. To avoid dust to go inside 8. How do you increase or decrease the size of plastics pallets? a. By adding or reducing material to the shredder b. By increasing or decreasing the barrel temperature c. By increasing or decreasing the speed of die face cutter d. By increasing or decreasing cooling temperature Page 70





___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________

________________________ DATE: __________________




________________________ DATE: __________________



WORKSHOP ACTIVITY #11-13

Practice Plant Operations PRACTICE YOUR OPERATIONS SKILLS! 1.

2. 3. 4.

5. 6.

Now that you have learned the basics of the Blown Film Extrusion process, it is time to practice your skills in running the plant and producing acceptable products. Strictly follow the Standard Operating Procedures (SOP) for each plant operations that you are going to perform. Use the worksheet tables and forms in the next pages to record your data. After each practice operations, write your general comment on the how well you have done your practice in the Conclusion & Recommendations page. Write down what you have done well, and what you should improve for the next practice. Enjoy practicing while being safe!

Page 72

Wo r k b o o k f o r B l o w n F i l m P r a c t i c a l C o u r s e WORKSHOP ACTIVITY #11-13—Practice Plant Operations

STANDARD OPERATING PROCEDURES (SOP)

PART A—SOP for Plant Run Preparations 1.

Read and understand carefully the JOB INSTRUCTIONS given by your instructor. (See Job Instruction #1).

2.

Switch on main power and pre-heat the blown film machine according to the temperature listed in the Job Instruction.

3.

Check the condition of the following: • •

Chilled water for barrel and reduction gear cooling (optional). Air supply for downstream equipments like nip rolls, winder and pressure roll.

4.

Prepare the materials to be used according to the Job Instruction.

5.

Prepare the following tools and equipments: •

Dial thickness gauge

•

Tape measure

•

Cutting knife for film

•

Cotton Gloves

•

Silicon spray

•

Brass or copper spatula

•

Cotton rags for die cleaning

•

Scouring paste

•

Guide twine or flat rope

•

Scouring pad

•

Allen wrench for die adjustment

6.

Prepare bobbins according to the width of the roll to be produced.

7.

Set the bobbin to the shafts of the winder and wrap around adhesive tape with the sticky surface exposed. Two turns are enough just to stick the film during change roll. Have at least five bobbins for replacements during roll change.

8.

Prepare the guide twine to the web path from the die to winder.

9.

Fill the hopper with the required materials.

10.

Change the screen in the screen changer if necessary.

Page 73


Standard Operating Procedures … continued

11.

Check the following blown film major parts’ conditions: •

Sizing basket — up and down movement

•

Haul-off unit — roll rotation and air pressure and functions

•

Collapsing device — functional adjustments

•

Corona treater — if flexo printing will run

•

Printing unit — functional adjustments and rolls rotations

•

11.

Winder — air pressure required for pressure roll and test for roll change

Wait for 1.5 hours till the “ready” indicator light lights up and verify again the temperature settings if the actual display temperatures correspond to the set temperatures. If yes, machine is ready to run. If not, check settings. If actual temperature is low, extend preheating time.

PART B—SOP Startup 1.

Open the shutter of the hopper.

2.

Switch-on the main motor and adjust the screw rpm to 10.

3.

Caution: Avoid facing the die during this stage. Melt material may spurt-out.

4.

Remove the initial extruded melt. This contains air trap in a material that should be removed.

5.

Increase screw speed to 30 rpm and remove the molten materials in the die. Wait until the high melt pressure drops.

6.

Do item 5 for 50, 75, and 100 rpm and back to 0.

7.

Clean the die and the die lip using scouring pad and scouring paste.

8.

Check die gap alignment. Align if off-centered by loosening and tightening centering screws. Use Allen wrench for adjusting the screws.

Page 74



9.

Open the blower damper at 30 degrees. Minimal air blown at the film for initial start.

10.

Open compressed air supply for inflating the bubble at minimum only.

11.

Make a loop on the film guide twine and have it ready.

12.

Switch-on again the main motor and set the screw speed to 25 rpm.

13.

Switch-on the haul-off nip and set the nip roll speed to 6-8 rpm.

14.

As the melt comes out let it cool to solidify and tie the film guide twine loop on that cooled lump.

15.

Pull gently the melt as it continue forming into a bubble.

16.

After the solid lump passes between the nip rolls, close the nip roll and let it do the pulling of the bubble.

17.

Temporarily closed the compressed air.

18.

Just pull the flat tube gently till it reaches the printing unit.

19.

Using the cutting knife, cut diagonally the film to make a pointed end.

20.

Insert this pointed end between the plate and impression roller of the printer.

21.

Pass the film between the open pressure roll and winder roll.

22.

Close the pressure roll pinching the film.

23.

Immediately, start the winder. Set minimum winding tension.

24.

Insert the film in between the rotating winder roller and bobbin with caution and start winding the film.

25.

Increase screw rpm gradually to the target rpm. (See Job Instruction.)

26.

Increase bubble diameter to its required lay-flat tube width. (See Job Instruction.)

27.

Increase nip roll speed according to the required film thickness. (See Job Instruction.)

28.

Switch-on corona treater if printing unit will run.

Page 75



PART C—SOP for Shutdown 1.

Close the shutter of the hopper.

2.

Switch-off corona treater if printing unit is running.

3.

Wait till the bubble starts to rattle. It is better to have a little material inside the barrel and die to seal-off the barrel form air getting inside.

4.

Gradually bring down the screw speed to 0 rpm.

5.

Switch-off the main motor.

6.

Bring down nip roll speed to 0 and switch-off.

7.

Open the nip roll.

8.

Bring down winder speed to 0 and switch-off.

9.

Open the pressure roll.

10.

Close the chilled water supply valve.

11.

Start lowering the temperature for 30 minutes.

12.

Switch-off the main power.

13.

Bring good rolls to the bag making area. Record the total roll weight produced in the Job Instruction.

14.

Bring all scrap to the recycling area. Record the total weight of the scrap in the Job Instruction.

15.

Return all tools and equipment to their proper places.

16.

Fill-up all the information needed in the Job Instruction.

17.

Submit the Job Instruction to your instructor.

Page 76



D ATA S H E E T ACTIVITY #11—Practice Plant Operations (LDPE) TRAINEE NAME

GROUP NO.

BLOWN FILM EXTRUSION PRODUCTION REPORT Machine No.

Product Description:

Date: Material Specifications No.

Type

Resin Name / Grade

Blending Ratio (%)

1 2 Machine Running Condition Monitoring Lot Number

1.

2.

3.

4.

5.

Heater Zone 1.1 Heater Zone 1.2 A c t u a l T e m p e r a t u r e ( o C )

Heater Zone 1.3 Heater Zone 2.1 Heater Zone 2.2 Heater Zone 3.1 Heater Zone 3.2 Heater Zone 3.3 Heater Zone 3.4 Heater Zone 4.1 MT

Extruder Screw Speed (rpm) Extruder Melt Pressure (bar) Air Ring

Pressure (KPa) Temperature (oC)

Haul-off Speed (mpm) Corona Treater Power (%) Printing Unit Motor Load (%) Winder Tension (N) Lay-on Pressure (bar) Contact Pressure (bar) Page 77



D ATA S H E E T ACTIVITY #11—Practice Plant Operations (LDPE) TRAINEE NAME

GROUP NO.

BLOWN FILM EXTRUSION PRODUCTION REPORT … continued Output Monitoring Lot Number

1.

2.

3.

4.

5.

Dismount Time Roll Number Length (m) Weight (kg) Total Scrap Weight (kg) Quality Check Monitoring Roll Number Measuring Point 1 T h i c k n e s s P r o f i l e ( µ m )

Measuring Point 2 Measuring Point 3 Measuring Point 4 Measuring Point 5 Measuring Point 6 Measuring Point 7 Measuring Point 8

Average Thickness (µm) Lay Flat Width (mm) Gusseted LFW (mm) Left Gusset Width (mm) Right Gusset Width (mm) Treating Level (OK/NOK) Tape Test (OK/NOK) Print Centering (OK/NOK) Print Repeat Length (mm) Clarity (OK/NOK) Color (OK/NOK) Defects (W/WO) Roll Disposition (Pass / Reject / On-Hold) Page 78



Wo r k b o o k f o r B l o w n F i l m P r a c t i c a l C o u r s e WORKSHOP ACTIVITY #11—Practice Plant Operations (LDPE)

QUESTIONS & EXERCISES 1.

If you want to raise the frost line height, what part of the machine are you going to adjust? a. winder tension b. the haul-off c. Air adjusting ring

2.

If you want to decrease the film thickness, what control are you going to adjust? a. haul-off speed b. winder speed c. main motor speed

3.

How are you going to adjust the speed in question #2? a. increase speed b. decrease speed

4.

If you want to reduce the lay-flat width, what are you going to do with the bubble? a. increase air inside b. decrease air inside

5.

How are you going to increase or decrease the air inside the bubble? Describe in your own words. ______________________________________________________ ______________________________________________________

6.

Is it necessary to use a film guide twine during start-up? Why? ______________________________________________________ ______________________________________________________

7.

Give at least 3 important speed adjusting controls of the blown film control panel. _________________________________________________ _________________________________________________ _________________________________________________

Page 79



Wo r k b o o k f o r B l o w n F i l m P r a c t i c a l C o u r s e WORKSHOP ACTIVITY #11—Practice Plant Operations (LDPE)


___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________

________________________ DATE: __________________




________________________ DATE: __________________




D ATA S H E E T ACTIVITY #12—Practice Plant Operations (LLDPE) TRAINEE NAME

GROUP NO.




Type

Resin Name / Grade

Blending Ratio (%)


1.

2.

3.

4.

5.








D ATA S H E E T ACTIVITY #12—Practice Plant Operations (LLDPE) TRAINEE NAME

GROUP NO.


1.

2.

3.

4.

5.

Dismount Time Roll Number Length (m) Weight (kg) Total Waste (kg) Quality Check Monitoring Roll Number Measuring Point 1 T h i c k n e s s P r o f i l e ( µ m )





Wo r k b o o k f o r B l o w n F i l m P r a c t i c a l C o u r s e WORKSHOP ACTIVITY #12—Practice Plant Operations (LLDPE)


What does melt pressure indicate? a. The pressure before the screen b. The pressure after the screen

2.

What does indicator means if the reading is high (500) _______________________________________________________ _______________________________________________________

3.

What happens to the output if the screen is clogged-up, increase or decrease? Why? _______________________________________________________ _______________________________________________________

4.

If the cooling of the barrel is not working, what do you think will happen to the bubble? _______________________________________________________ _______________________________________________________ _______________________________________________________

5.

If the rolled film in the shaft is hard to removed, what must be the probable cause? _______________________________________________________ _______________________________________________________

6.

How are you going to prevent the problem in #5 from happening during operations? _______________________________________________________ _______________________________________________________

7.

Give at least 2 causes why bubble is pulsating. _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________

Page 83



Wo r k b o o k f o r B l o w n F i l m P r a c t i c a l C o u r s e WORKSHOP ACTIVITY #12—Practice Plant Operations (LLDPE)


___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________

________________________ DATE: __________________




________________________ DATE: __________________




D ATA S H E E T ACTIVITY #13—Practice Plant Operations (HDPE) TRAINEE NAME

GROUP NO.




Type

Resin Name / Grade

Blending Ratio (%)


1.

2.

3.

4.

5.








D ATA S H E E T ACTIVITY #13—Practice Plant Operations (HDPE) TRAINEE NAME

GROUP NO.


1.

2.

3.

4.

5.

Dismount Time Roll Number Length (m) Weight (kg) Total Waste (kg) Quality Check Monitoring Roll Number Measuring Point 1 T h i c k n e s s P r o f i l e ( µ m )





Wo r k b o o k f o r B l o w n F i l m P r a c t i c a l C o u r s e WORKSHOP ACTIVITY #13—Practice Plant Operations (HDPE)


Give at least 2 causes of die lines. _______________________________________________________ _______________________________________________________

2.

Give at least 2 causes of uneven film thickness. _______________________________________________________ _______________________________________________________

3.

What are you going to do with the die if the film wall at the right side is thicker than the left side? _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________

4.

Give at least 2 causes of film blocking. _______________________________________________________ _______________________________________________________

5.

Give at least 3 common problems of blown film process. _______________________________________________________ _______________________________________________________ _______________________________________________________

Good Luck!!!!!

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Wo r k b o o k f o r B l o w n F i l m P r a c t i c a l C o u r s e WORKSHOP ACTIVITY #13—Practice Plant Operations (HDPE)


___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________

________________________ DATE: __________________




________________________ DATE: __________________



Formulas for Blown Film Computations Blow Up Ratio (BUR)

BUR =

Bubble Diameter, D 2 Die Diameter, D1

D2

2

D2

= LFW×

D2

= 0.637 × LFW

π

D1

where: LFW = Lay Flat Width, cm D1 = the die diameter, cm D2 = the bubble diameter, cm

Die

Theoretical Bag Film Weight t =thickness, cm

W bag = w× L × t × 2 × ρ where: W bag = theoretical bag film weight in grams w = width of the bag, cm L = cut length of the bag, cm t = thickness of the film, cm ρ = material density, gm/cm³

Film Bag

L

W

Page 89


Formulas for Blown Film Computations Theoretical Roll Weight

W bag = w× L × t × 2×

w

t

where: W bag = theoretical bag film weight in grams w = width of the bag, cm L = cut length of the bag, cm t = thickness of the film, cm ρ = material density, gm/cm³

Rolled Film

Theoretical Output

•

Computing for Output Rate per RPM of a Given Output:

Output Rate per RPM

=

Output Rate, kg per hour Screw Speed, RPM

Output Rate = ___________ kg/hr/RPM •

Getting the Needed Output of a Desired Screw RPM Target Output

=

Desired Screw Speed, RPM

× Output

Rate per RPM

Target Output = __________ kg/hr

Page 90


Formulas for Blown Film Computations Theoretical Take-off Speed

Theoretical Take - off Speed =

Output Rate LayFlatWidth × 2 × Thickness × Density

Theoretica l Take - off Speed (cm/min)

=

Output Rate (g/min) LFW (cm) × 2 × t (cm) × ρ (g/cm 3 )

Page 91


Glossary of technical terms for Blown Film Air-ring

A circular component of a blown film system that directs cool air up the sides of a tubular blown film bubble to cool and solidify the melt.

Alloy

Plastics made by mechanically blending two or more different polymers.

Additive

Substance compounded into a resin to modify its characteristics (i.e., antistatics, stabilizers, plasticizers, flame retardants, etc.).

Aging

The process of exposing the film to a controlled environment for an interval of time.

Ambient conditions The existing conditions of temperature and humidity in any building or room. Amorphous

A polymer is said to be amorphous when its molecules are in long random or coiled chains. Amorphous plastics tend to be transparent, and are more soluble than crystalline plastics. Having no crystalline structure.

Anilox Roll

Mechanically or laser-engraved roll for transfer of ink to printing plate. Specifications are in lines per inch and cell volume (ex. 800-line anilox will transfer a thinner film of ink than a 300-line anilox).

Antiblock

An additive used in plastic, generally at 1 or 2% that roughens the film surface from adhering to each other. The most common anti blocks are based on clay by-products.

Antioxidant

Additives that prevent oxygen from causing molecular breakdown in polymers.

Anti-static agent A substance that can be applied to the surface of a plastic article, or incorporated in the plastics from which the article is to be made. Its function is to render the surface of the plastic article less susceptible to accumulation of electrostatic charges which attract and hold fine dirt or dust on the surface of the plastic article. Auxiliary equipment The types of equipment used to enhance, support or add to the precision and efficiency of injection, extrusion or other primary processing machinery. (Continued on page 93)

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(Continued from page 92)

Arc

A luminous glow by the flow of electric current through ionized air, gas or vapor between two separated electrodes or contacts.

Band heater

Electrical heating units fitted to extruder barrels, adaptors, dies, nozzles, etc., utilized for heating the polymer to a desired temperature.

Barrel

A metal tube that houses a rotating screw, or sometimes a ram, in which plastic is heated before extrusion or moulding.

Barrier layer

A layer of material in film, sheet or a blow molded container that prevents the passage of moisture, flavors or certain gases.

Biaxial Orientation The process of stretching a hot plastic in two directions under conditions resulting in molecular orientation in two directions. Bleed

(1) To give up color when in contact with water or a solvent. (2) Undesired movement of certain materials in a plastic (e.g., plasticizers in vinyl) to the surface of the finished article or into an adjacent material; also called migration. (3) An escape passage at the parting line of a mold, like a vent but deeper, that allows material to escape or bleed out.

Blocking

Substrate sticking to itself after being printed and rewound. Image often transfers to back-side of other label.

Bloom

(1) A non-continuous surface coating on plastic products that comes from ingredients such as plasticizers, lubricants, antistatic agents, etc., which are incorporated into the plastic resin. It is not always visible. Bloom is the result of ingredients coming out of solution in the plastic and migrating to its surface.

Blooming

Migration of additives to the surface of the film

Blown film

Film made by extruding molten plastic through a circular die, and forming an inflated, tubular bubble that moves through a cage as it cools, to be sliced open, collapsed and formed into rolls.

Breaker plate

A metal plate installed across the flow of the stock between the end of an extruder screw and the die, with openings through it such as holes or slots. It usually is used to support a screen pack.

Bubble

In blown film referred to as the inflated molten tube. (Continued on page 94)

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Cage, blown film A structure, usually with rollers or roller beads, through which a bubble of blown film passes at it is extruded and cooled. Calcium carbonate (CaCO3 ) A filler and extender used in thermoplastics. It occurs naturally in the form of minerals such as calcite, chalk, limestone, marble, and whiting. Calendering

The making of sheet or film with high-quality surface characteristics by passing molten plastic from a kneader over a series of rollers that flatten and/or emboss it.

Caliper

The thickness of the substrate usually measured in thousandths of an inch (mils). "Microns" (metric) are specified for some substrates.

Cartridge heater Cylindrical electrical heater used to heat nozzles, hot runners and moulds in injection and compression molding. Cast film

A film process, used where good cosmetics are needed, in which molten plastic flows over a chilled roll or through a quench bath.

Chiller

A self-contained system comprised of a refrigeration unit and a coolant circulation mechanism consisting of a reservoir and a pump. Chillers maintain the optimum heat balance in thermoplastic processing by constantly re-circulating chilled cooling fluids to molds, machines, etc.

A measure of how slippery a film is. Coefficient Coefficient of friction, COF of friction is a number that expresses, for a given surface, the ratio of the force required to slide an object over a frictionless surface to the force required to slide the same object over the actual surface. The COF, or slip properties, of film are important in determining how that film will perform on conversion equipment and in final form such as in open ability or stacking. This test determines the ability of film to slide over itself and is used to determine the effectiveness of slip additives incorporated into resins. Both static (starting) and kinetic (sliding) friction are measured. Coextrusion

A process whereby two or more plastics are extruded through one die, to produce a material combining their properties.

A pair of frames that gradually collapse the film tube and Collapsing frame guide this flattened tube smoothly into the nip rolls. (Continued on page 95)

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Compound

Plastics that has colorants, additives or reinforcements added in a compounding extruder or mixer.

Compression ratio In an extruder screw, the ratio of volume available in the first flight at the hopper to that in the last flight at the end of the screw. Concentrate

A measured amount of additive (e.g., dye, pigment, foaming agent, anti-static agent, flame retardant, glass reinforcement, etc.) that is incorporated into a predetermined small amount of plastic. This (the concentrate) then can be mixed into larger quantities of plastic to achieve a desired color or end-property.

Copolymer

A polymer produced by reacting two different monomers together to form long chains.

Crystallinity

Polymers are said to be crystalline when their molecules are in a regular, repeated lattice arrangement that makes them relatively dense; non-transparent (because the crystals scatter light); resistant to solvents or to chemical attack; and having a very sharp melting point.

Dart impact strength A measure of a plastic's resilience, especially film's, measured with a special dart or steel ball dropped on it. Degradation

A deleterious change in the chemical structure or physical properties of a plastic, caused by exposure to heat, light or other agent.

Density

Weight per unit volume of a substance, expressed in grams per cubic centimeter. Also called Specific Gravity. Polyethylene ranges between .9100 - .9650. Water = 1.000, anything less than that floats; greater than that will sink. LDPE is low density polyethylene, HDPE is high density polyethylene. Density is a basic molecular property that can affect many essential physical properties of a polymer. Density, in part, is a function of the crystalline structure of the polymer. It is an excellent means of identifying a product, following physical changes, and determining uniformity.

Die Line

A line or series of lines on the film surface that run in the machine direction. If there are numerous die lines , it is generally due to the build-up of oxidized materials on the die. If the die line is a single, deep line it is generally due to a foreign object on the die. (Continued on page 96)

Page 95



Die-lip

In blown film, the edge of the circular dies.

Discoloration

Any change from the original color, often caused by overheating, light exposure, irradiation, or chemical attack.

Dispersion

Finely divided particles of a material in suspension in another substance.

Doctor blade

Thin, flexible steel, plastic or composite blade that passes over a gravure plate cylinder or flexographic anilox roll wiping off excess ink before ink is transferred to substrate or plate.

Downstream equipment In extrusion, winders, haul-offs, saws, vacuum sizing tanks and other equipment that trims, cuts and finishes extruded film or shapes. Draw down ratio The ratio of the thickness of the die opening to the final thickness of the product. Drive

The entire electrical and mechanical system used to supply mechanical energy to the input shaft of a gear reducer. This includes the motor, constant or variable speed belt system, flexible couplings, starting equipment, etc.

Dryer

A device to absorb and/or drive off moisture from resin powder or pellets that, if heated while still containing traces of moisture, would make defective parts.

Dynes

A unit of energy, also a unit of measure for surface tension (treat).

Elastomer

A plastic with some of the elastic, flexible properties of natural rubber.

Elasticity

The elasticity of material by virtue of which it tends to recover its original size and shape after deformation. If the strain is proportional to the applied stress, the material is said to exhibit Hookean or ideal elasticity.

Elongation

The fractional increase in length of a material stressed in tension.

Environmental Stress Cracking (ESC) The susceptibility of a thermoplastic article to crack or craze when stressed, in the presence of surfaceactive agents or in other environments. Extruder

A machine that melts plastic powder, pellets or flake, possibly (Continued on page 97)

Page 96



with colorants and additives added. The basic machine consists of a barrel, heater units around it, a drive system, and a fluted screw inside to move and pressurize the plastic from the throat to the extruder die. Extrusion

The process of melting plastic pellets, flake or powder by means of heat and pressure, then forcing the melt through a die to produce film or a three-dimensional profile shape.

Fabricate

To work a material into a finished form by machining, forming or other operation.

Feedstock

Chemical source from which monomers for polymers are derived.

Feed throat

The point at which resin or additives is added into an extruder or injection unit.

Feed section

First section or zone of an extruder screw, which is fed from the hopper and conveys solids to the melting zone.

Feed zone

A passage wherein a material passes through going down the screw.

Filler

Material such as calcium carbonate or wood flour used with plastics to reduce costs and to impart additional mechanical properties.

Fines

Very small particles (usually under 200 mesh) accompanying larger grains, usually of molding powder.

Fish-eye

An unmelted lump of plastic in a melt, especially visible in clear films.

Flexography

A form of rotary web letterpress using flexible rubber or photopolymer plates and fast-drying solvent, water-based or UV inks. Photopolymer plates with raised surfaces that transfer ink to the substrate are mounted to print cylinders using double faced adhesive (stickyback).

Frost line

The point in a blown film bubble at which the film tube reaches its maximum diameter, and acquires a frosted appearance as the plastic falls below its softening temperature.

Friction

The resisting forces that arise when a surface of the film slides or tends to slide over an adjoining surface of itself. (Continued on page 98)

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Flame retardant A chemical compounded into a resin to make it fireresistant. Flight

The outer surface of the helical ridge of metal on an extrusion or injection molding screw.

Gauge

Film thickness express in mils or microns ().

Glass Transition Temperature The temperature below which a given plastic behaves like glass, being strong but brittle. Gear Reducer A combination of gears enclosed in a case. Gel Count

Gels are hard, unmelted particles randomly distributed throughout the film. Gels are unattractive and, in most cases, will be detrimental to film downgauging. The types of imperfections vary, but four of the most common are pinpoint, arrowhead, fisheyes, and oxidized or discoloured gels. As different applications will tolerate varying levels of film purity, a gel count test gives the producer or extrusion shop indications as to end-use expectations. This test is very useful as a quality control tool.

Gloss

A measure of the reflectivity (shininess) of a film's surface of light from a given angle, in this case - 45 degrees. The higher the number, the shinier the film. Gloss can impact desirability of consumers to purchase the film product or something packaged within it. Gloss in film can be optimized by adjustment of extrusion parameters. Once processing conditions are perfect, changing resins to a higher melt index and higher density at a constant MW and MWD will generally results in better gloss.

Gusset

A fold on the sides of an extruded film tube. May also be done at the bottom of the formed bag.

Haze

A measure of the clarity or transparency of film. It is expressed as the amount of light that is not transmitted through a film sample. The lower the number, the higher the clarity. In certain applications, high clarity and minimal haze or frostiness is desirable. This is the case in many packaging applications where good clarity enhances the sales. Both surface roughness and polymer structure diffuse light as it passes through film and cause the hazy appearance. Extrusion parameters can be optimized to improve haze along with proper resin selection. (Continued on page 99)

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Half-tone

A printed image of a continuous-tone original (like a photograph) that is composed of tiny dots to create the illusion of continuoustone though printed with only single density. Halftones are reproduced in screen values for flexographic printing from 80 line (carton, fiber board and course papers) to 300 line (high gloss, smooth finish papers). The majority of high quality flexographic printing uses 133 to 150 lines screened halftones.

Heater band

A band, normally of ceramic, mica or metal that is heated, and transfers its heat to the barrel of an extruder.

Hopper dryer A combination feeding and drying device for extrusion and injection molding of thermoplastics. Hot air flows upward through the hopper containing the feed pellets. Hydrophilic

Tending to absorb water.

Hydrophobic

Tending to absorb little or no water.

Hygroscopic

Tending to absorb atmospheric moisture.

Impact resistance A measurement of the strength of film and its ability to withstand the shock of a falling "dart" without breaking, in other words, puncture resistance. Expressed as the gram weight of the heaviest dart which doesn't break the film when dropped from a specific height. The impact strength of film can be determined and applied to end-use properties through a number of different impact tests. Knowing these results aids in determining which particular resins are best suited for high-strength applications such as the construction and agriculture market. Internal Bubble Cooling, IBC Injection of cold air into a tubular bubble of a blown film, so that it cools and solidifies. Laminate

Product made by bonding two materials or two layers of one material.

L/D ratio

The length-to-diameter ratio of a screw, which affects how it melts a given plastic.

Land

(1) The bearing surface along the top of the flights of a screw in a screw extruder. (2) The surface of an extrusion die parallel to the direction of melt flow.

Lay flat

Measurement of a film sample in the TD on a flat ruler or tape (Continued on page 100)

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measure. Lay Flat Width, LFW The width of the tubular film when it is flattened. Light resistance The ability of a plastics material to resist fading after exposure to sunlight or ultraviolet light. Light transmission

The amount of light that a plastic will allow to pass.

Linear Low Density Polyethylene, LLDPE A process variation of low density polyethylene. It enables high draw down-gauging in extruding, while maintaining high film strength. Low Density Polyethylene, LDPE A partially crystalline, lightweight thermoplastic, polymerized form ethylene gas at controlled temperature and pressure. Lubricant

Additive to plastic resin to promote mixing and improve flow properties.

Machine Direction, MD The direction of the film which corresponds to the way it came out of the extruder. On rolled film it is the length of the film. Some film properties vary according to film direction. Masterbatch

A plastics compound that includes a high concentration of an additive or additives. Masterbatches are designed for use in appropriate quantities with the basic resin or mix so that the correct end concentration is achieved. For example, color masterbatches for a variety of plastics are used extensively, as they provide a clean and convenient method of obtaining accurate color shades.

Melt

Term to describe molten plastic.

Melt fracture

An instability in the melt flow through a die, starting at the entry to the die. It leads to surface irregularities on the finished article such as a regular helix or irregularly spaced ripples.

Melt Index

The amount, in grams, of a thermoplastic resin that can be forced through a 0.0825 inch orifice when subjected to 2160 grams force in 10 minutes at 190ºC.

Melt strength

The strength of a plastic while in the molten state.

Melting Point The temperature at which a resin changes from a solid to a liquid. (Continued on page 101)

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The main section of a screw, which handles plasticising by heat and pressure.

Melt zone

Metallocene catalyst A category of Ziegler-Natta catalysts for polymerizing polyolefin. The structure of its own molecules orients the olefin monomers into polyolefin polymers with tightly repeatable shapes and properties. Metering zone The relatively shallow discharge end of a screw. Metering screw

An extrusion screw that has a shallow constant depth and a constant pitch section over, usually, the last three to four flights.

Metering section A relatively shallow portion of an extruder screw at the discharge end with a constant depth and lead, and having a length of at least one or more turns of the flight. Mica

Natural, plate-like silicate mineral used as a reinforcement or mineral filler.

Mil

One thousandth of an inch (0.001" or 0.001in.). Measure of the film thickness.

Melt Index, MI Melt index is commonly used to classify polymeric resins. Melt index uniformity is essential in maintaining control of processing parameters, and melt index is inversely proportional to molecular weight or polymeric chain length. Melt index heavily influences physical properties. Modulus of Elasticity The ratio of stress to strain in a material that is elastically deformed. Moisture Vapor Transmission The rate at which water vapor permeates through a plastic film or wall at a specified temperature and relative humidity.

The ability of a material to resist absorbing ambient Moisture resistance moisture. Molecular weight The sum of the atomic weights of all atoms forming a molecule.

A measure of the relative amounts of Molecular Weight Distribution polymers with different molecular weights within a batch of material. This measure may be indicated by the ratio of the (Continued on page 102)

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weight-average molecular molecular weight.

weight

to

the

number-average

Monomers

Single molecules, in gaseous or liquid form, that can be joined in chains to form polymers, the building blocks of plastics.

Nip

Line of contact between two rollers.

Nip rollers

A pair of rolls at the top of a blown film tower that close the film bubble, and also, by their action, regulate the rate at which molten plastic is pulled from the extrusion die. A set of rollers used to compress the plastic bubble into a sheet, or to feed the film to the winder at the proper tension.

Nitriding

Hardening process for steel screws and barrels, also referred to as ion nitriding.

Nylon

Term for the family of polyamide polymers, first synthesized by DuPont scientists in 1938. These crystalline plastics are tough and offer good heat and chemical resistance.

ODR

Term used in pouching material - Odor Transmission Rate. How fast the odor will pass through the substrate.

Olefins

A group of unsaturated hydrocarbons of the general formula CnH2n, and named after the corresponding paraffin by the addition of “ene” to the stem. Examples are ethylene and propylene.

Opacity

The amount of light that will penetrate through a colored item. Opacity is higher with thicker films or with greater loading of color. It has nothing to do with the particular shade or color of the film.

Opaque

Description of a material or substance that will not transmit light; opposite of transparent. Materials that are neither opaque nor transparent sometimes are described as semi opaque, but are more properly classified as translucent.

Oscillating nip rollers Collapsing system on top of a blown film tower that rotates back and forth to randomize, or distribute, gauge variations in the film being blown. Orientation

The direction in which polymer chains lie, or are made to flow, in plastic film, sheet or parts. (Continued on page 103)

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Overs/Unders Copies printed varying from the specified quantity. Depending on the quantity ordered, the standard in our industry is usually 10%, unless otherwise specified. Oxidation

A chemical process where a compound combines with oxygen to form a different compound.

Pitch

The distance from any point on the flight of a screw line to the corresponding point on an adjacent flight, measured parallel to the axis of the screw line or threading.

Plastic

A material of organic origin, of high molecular weight, that can be shaped by being made to flow through the application of heat and/or pressure, and that will set solid after the forming process. The word derives from a Greek root, plassein, which means to mold.

Photopolymer A plastic that cures in response to ultra violet or another form of light. Permeability

(1) The passage or diffusion of a gas, vapor, liquid or solid through a barrier without being physically or chemically affected. (2) The rate of such passage.

Pigment

A coloring agent mixed with plastic material prior to processing to provide a uniform color.

Pin holes

Small random holes found in a film.

Plate cylinder The cylinder of a press on which the plate is mounted. Plate Gap

The space left when the plates are wrapped around the cylinder. No copy or image can be printed in this area that is usually 1/8" wide.

Plastics tooling

Tools (e.g., dies, jigs, fixtures, etc.) for the metal forming trades constructed of plastics, generally laminates or casting materials.

Polymer

Compound forming a chain of chemically linked monomers, or single molecules; a chemist's description for a basic plastic.

Polyethylene

In its pure form, a chemically stable plastic material. Used in film form to make sleeves for photographic materials and other uses. A cheaper alternative to polyester film. (Continued on page 104)

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Polyester

A thermoset or thermoplastic material, made by polymerizing any of a range of ester monomers, usually with properties of toughness, stiffness and/or a high melting point.

Plastic usually abbreviated as PVC, or sometimes Polyvinylchloride, PVC 'vinyl'. Not as chemically stable as some other plastics. It can emit acidic components which damage cellulosic materials. Added chemicals called plasticizers are also used to make PVC more flexible. These also damage library materials. Preheating

The heating of a compound prior to molding in order to facilitate the operation, reduce the cycle, and improve the product.

Primary processing equipment equipment Machinery that actually moulds, extrudes or initially forms plastic parts and products. Proof

A facsimile image of the final printed piece created before presswork begins. Used for evaluation by production staff and customer prior to printing.

Purging

Cleaning one color or type of material from the cylinder of an extruder by forcing it out with a new color or material to be used in subsequent production. Purging materials also are available.

Recycle

Material from flash, trimmings, scrap, rejects, etc., that can be ground up or repelletized and fed back into the processing machine.

Register

The fitting of two or more images on top of each other in exact alignment.

Reprocessing Recycling of plastics back into processible material, usually through pulverizing or re-extrusion. Resin

Term for plastics raw materials in powder, pellet or flake form.

Rewinding

The process of rewinding a roll of substrate to produce a proper size for the customer, to splice the ends together and/or to remove defects.

Rheology

The scientific study of the deformation and flow of matter, particularly as it moves through a processing line.

Rotogravure

The printing process that involves the principal of engraving. An engraved cylinder is immersed in a fluid ink; the ink is wiped or (Continued on page 105)

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doctored from the surface of the cylinder; and the ink left in the recessed area of the cylinder is transferred to the substrate. Scrap

Any product of a molding operation that is not part of the primary product. Scraps in blow molding such as rejected parts and sprues usually can be reground and remolded.

Screen

A mesh plate that eliminates impurities from a melt stream.

A device for replacing Screen changer interrupting the extrusion process.

filtering

screens

without

Screw

The rotating, flighted part of an extruder or injection unit, which, in turning rapidly helps to melt, and convey, the plastic from the hopper throat to the die or nozzle.

Shear

An effect whereby parts of a melt separate and move against each other. This is desired and essential in the heating stage, but excessive shear produces breakdown of a plastic's properties.

Shrinkage

A measurement of the percent of film shrinkage under a controlled temperature and time interval. As a result of the manufacturing process, internal stresses may be locked into the film which can be released by heating. The temperature at which shrinkage will occur related to the processing techniques employed to manufacture the film and may also be related to a phase transition in the base resin. The magnitude of the shrinkage will vary with the temperature of the film Shrinkage of a particular material produced by a particular process may be characterized by this test method by making measurements at several temperatures through the shrinkage range of the material. This property is important to consider when handling film in downstream equipment that requires heating.

Silicone spray Chemical derived from silica; used in molding as a release agent and a general lubricant. Silicone

Chemical derived from silica; used in molding as a release agent and a general lubricant.

Slip agents

Substances added to make the sliding action easier. These additives are designed to bloom to the surface and provide an invisible coating on the film, reducing the coefficient of friction. Fatty acid amines are an example which is widely used in film (Continued on page 106)

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extrusion. Slitting

Cutting printed sheets or webs into two or more sections by means of cutting wheels on a press or rewinder.

Smear

Film surface defect, usually V-shaped, and protrude from the film surface.

Spiral die

A die used for blown film that brings the molten plastic through spiral channels from an extruder to the die-lip, ensuring a homogeneous melt when the melt emerges to form the bubble.

Solvent

Any substance, usually a liquid that dissolves other substances. Liquid that dissolves a solid. In ink, the evaporation of solvent leaves the solids behind as an ink film on the substrate.

Specific gravity The density (mass per unit volume) of any material divided by that of water. Spider

A term used to denote the membranes supporting a mandrel within the head/die assembly.

Stabilizer

An ingredient used in the formulation of some plastics to assist in maintaining the physical and chemical properties of the compounded materials at their initial values throughout the processing and service life of the material.

Stabilizer, heat

A chemical additive that prevents deterioration of plastic during heating.

Stabilizer, light A chemical additive that helps screen plastic from the deleterious effects of ultra-violet light. Substrate

Any printing surface (paper, polypropylene, polyester, PVC, PETG, etc.).

Any method of treating a material so as to alter the Surface treating surface and render it receptive to inks, paints, lacquers, and adhesives, such as chemical, flame, and electronic treating. Surging

Unstable pressure build-up in an extruder leading to variable throughput.

SWS, Single Wound Sheeting One single thickness of plastic being wound on a core. (Continued on page 107)

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Talc

A natural, hydrous magnesium silicate used in plastics as reinforcing filler.

Tear strength

A measurement of the strength of a film and its ability to resist tearing under specific conditions. Tear strength is the force required to continue an initially started slit across a film specimen. This widely used test has some value in quality control of film production, but is not a very useful indicator of the strength of film in service.

Tensile properties A measurement of the strength of a film and its ability to withstand stretching or pulling. Tensile properties which include tensile strength at yield, ultimate tensile (or break tensile strength) , and elongation, are tests used to determine relative strength of different films. Yield strength measures the point at which the film, when, stretched, will not resume its original shape. Ultimate tensile is the measure of a load that will cause the film to rupture. Both yield and ultimate measurements are measured in lb/ in2 of a cross-sectional area of useful information on how polymers process and perform. For example, polyolefin generally tend to process with easier and wider MWD and improved drawdown. Within a given family of resins, many film properties can be correlated with molecular properties. Telescoping

Lateral shifting of layers of film, causing the edge of the roll to have a conical shape appearance.

Thermal Stress Cracking Crazing and cracking of some thermoplastic resins that results from overexposure to elevated temperatures. Thermocouple A temperature-sensitive device consisting of a pair of wires of dissimilar metal welded together at one end. The electric current created at different temperatures is measured by a calibrated potentiometer. Thermoplastic A polymer that can be heated and reformed any number of times. Thermoset

A polymer that, once heated and formed, cannot be re-melted without fundamental degradation, because its polymer chains are heavily cross-linked.

Tint

A small amount of color added to a plastic film. You can see through the film, yet there is still a noticeable color (Continued on page 108)

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Tower

A rigid metal frame or structure that holds the collapsing frame and the nip rolls.

Transducer

An input/output electronic device that can measure load or pressure when placed in a sensor cell adjacent to the flow path of a melt.

Translucent

Descriptive term for a material or substance capable of transmitting some light but not clear enough to be seen through.

Transparent

Descriptive term for a material or substance capable of a high degree of light transmission (e.g., glass).

Traverse Direction (TD) The direction at right angle to the direction of the extrusion (MD). Film is tougher in this direction. Treat

The process of using high frequency electrical discharge to oxidize the film surface, thereby making the surface more acceptable of printing and other substances.

Tube

Shape of molten plastics extruded from the die during blown film process.

UV Inhibitor

Used to inhibit or prevent degradation of the film from ultraviolet radiation sources such as sunlight and fluorescent lighting.

A chemical additive that selectively absorbs or Ultraviolet (UV) Stabilizer filters out light waves at the ultra violet end of the spectrum, protecting plastics from their harmful effects (embrittlement, discoloration, crazing and disintegration). Vicat Softening Temperature Measurement of the heat distortion temperature of a plastic material. Also called the heat deformation point. Vinyl

Common abbreviation for polyvinyl chloride, a plastic used for some packaging and house wares but particularly for construction items such as pipe, window frames, doors and siding for houses. The term is also sometimes applied to other plastics in the range of vinyl copolymers.

Virgin resin

Plastic resin that has never been previously heated or formed.

Viscosity

The property of an ink defined as the resistance to flow or simply the fluidity or thickness of the ink.

Water absorption

The ability of a thermoplastic material to absorb water (Continued on page 109)

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from an environment. WVTR, Water Vapor Transmission Rate Term used in pouching material Water Vapor Transmission Rate. How fast moisture passes through the substrate Weld Lines

Also Weld Marks or Flow Lines. Marks on a molded plastic piece made by the meeting of two flow fronts during the molding operation.

Wetting Tension The ability of polyolefin films to retain inks, coatings, adhesives, etc. is dependant upon the character of the surface and can be improved by surface treating techniques such as corona discharge or flame treatment. Wetting tension is utilized to determine the degree or level of treatment applied by establishing a correlation between surface tension (wetting tension) and treatment level. Winder

A mechanical equipment of blown film machines that wind up the lay flat tubular film that has been taken off.

Wrinkles

Imperfections in plastic sheeting that has the appearance of a wave or a crease

Yellowness Index A measure of the tendency of plastics to turn yellow upon exposure to heat or light. Yield

The area of film at a given thickness produced from a given weight of resin.

Yield Value (Yield Strength) The lowest stress at which a material undergoes plastic deformation. Below this stress, the material is elastic; above it, the material is viscous. Young’s Modulus of Elasticity The modulus of elasticity in tension; the ratio of stress in a material subjected to deformation. Ziegler-Natta catalysts Large family of polymer catalysts discovered by Karl Ziegler, and developed by Giulio Natta, with whom he shared the Nobel Prize for their work in 1963. Zippering

An effect seen in blown film where a puncture or defect results in a visible tear line appearing in the film surface.

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Blown Film Workbook Draft

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