STUDY OF THE MEDIUM DENSITY POLYETHYLENE MECHANICAL MILLED WITH THE GRAPHITE POWDER
CHEAH WOI LEONG
TABLE OF CONTENTS TITLE PAGE TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES LIST OF APPENDIX LIST OF ABBREVIATIONS CHAPTER 1
CHAPTER 2
Pages i ii iii iv v vi
INTRODUCTION 1.1 Research Background 1.2 Problem Statement 1.3 Objectives
1 2 2
LITERATURE REVIEW 2.1 Polyethylene-graphite Polyethylene-graphite nanocomposite 2.2 Graphite 2.3 Polyethylene (PE) 2.4 Medium Density Polyethylene (MDPE)
3 4 4 6
LIST OF TABLES
Tables No.
Page
3.1
9
Instruments and method
LIST OF FIGURES
Figures No.
2.1 3.1 3.2
Polyethylene chain with side branches Condition for constructive interference Sample preparation and etching process
Page
6 11 13
LIST OF APPENDIX
Tables No.
Page
A1 A2
17 20
commercially produced metallocenes Gantt chart proposal 2010
LIST OF ABBREVIATIONS
Abbreviations
DENT FNCT FTIR HDPE IUPAC MA MD MDPE mf MG ML MM ms PE
Double Edge Notched Tensile Full Notched Creep Tensile Fourier Transform Infrared Spectroscopy high density polyethylene International Union of Pure and Applied Chemistry Mechanical Alloying Mechanical Disordering Medium Density Polyethylene mass at the end of temperature, T Mechanical Grinding percentage loss of mass Mechanical Milling mass at the start, before heating Polyethylene
CHAPTER 1
INTRODUCTION
1.1
Research Background
Many researchers do relate the conductivity to polymer matrices with respect to the presence of polymer groups, polymer surface tension and different blends of polymer. One influencing factor that has not been dealt with is the compatibility of polymer
diffraction (XRD), Scanning electron microscope (SEM), and Thermogravimetry (TGA).
1.2
Problem Statement
According to the research of Hamouda et al. (2006). Creep fracture by slow crack growth is studied in a medium density polyethylene at
60̊ C and 80̊ C. Whereas
elastic – plastic fracture mechanics load parameters fail to provide a unique temperature-independent correlation, that of the fracture mechanics for creeping solids is proved to be relevant since this parameter correlates very well with the time to failure.
Slow crack growth (SCG) behaviour has been investigated under creep conditions in a medium density ethylene – butene copolymer (MDPE) on both axisymmetrical Full Notched Creep Tensile (FNCT) and Double Edge Notched Tensile (DENT) samples tested at 60̊ C. Fracture Mechanics for Creeping Solids approach was attempted for
Chapter 2
LITERATURE REVIEW
2.1
Polyethylene-graphite Nanocomposite
This research conducted a mixture of both a new and modified research. The research will carry out the characterization of the MDPE-graphite composite and determine the chemical properties and mechanical properties. Some of the researchers have also
2.2
Graphite
In recent years, The raw materials most frequently used in graphite manufacturing are some types of coke, carbon black and natural graphite, which are ground, sieved and added to a binder. The paste at this stage is homogenized and placed in molds or passed through drawing frames, sufficiently compacted. The material is then baked slowly, protected by coke powder, at a temperature of at least 10 00 ◦C for complete elimination of volatile particles from the binder and to transform the remaining particles into coke.
In principle, graphite is normally classified by grain size. The grain size is used as a criteria because most of the other properties and characteristics of graphite are related directly or indirectly to the grain size and orientation. Nowadays, the market offers graphite classes with average grain sizes under 1µm up to 20µm.
Due to its low mechanical strength, graphite is considered to be easily machined.
Polyethylene (PE) is a natural, organic, thermoplastic homopolymer which does not melt at one particular temperature into a clean liquid. Instead it becomes increasingly soft and ultimately turns into a very viscous, tacky molten mass. It has a low Tg as strong intermolecular cohesive forces are absent and the substituent group (CH2) present in it is not bulky. PE is a polymer consisting of long chains of the monomer ethylene (IUPAC name ethene). Polyethylene is classified into several different categories based mostly on its density and branching. The mechanical properties of PE depend on variables such as the extent and type of branching, the crystal structure, and the molecular weight. (Kosuri et al. , 2008) Some classifications of PE include:
· Ultra high molecular weight PE (UHMWPE) · High density PE (HDPE) · Cross-linked PE (PEX) · Medium density PE (MDPE) · Linear low density PE (LLDPE)
2.4
Medium Density Polyethylene (MDPE)
Medium-density polyethylene, MDPE, is a semi-crystalline thermoplastic polymer which has been increasingly used for fabrication of plastic pipes for water and gas distribution systems. (Peres et al. , 2010)
MDPE viscoelastic characteristics at room temperature, it is susceptible to long term creep fracture by means of a slow stable crack growth mechanism. (Brown, 2007)
According to the research of Mohammad (2008), he investigated the sole effect of each parameter and their combination on maximum stress produced in MDPE gas pipes and their sockets which are made from PE100. MDPE can be used for water pipe, gas pipe, MDPE plastic pipe and so on. It is known that MDPE pipes offer many advantages over traditional ductile iron and steel pipes. These advantages include flexibility, coilability, high ductility, light weight, corrosion resistance, and reduced installation costs. These features provide both performance and economic benefits
Figure 2.1 shows a schematic picture of such a side branching chain; the branches radiate three-dimensionally, just as the branches of a tree point in all directions from various places along the trunk. The presence of such side branches is a reason for variations in a number of important physical properties (such as density, hardness, flexibility or melt viscosity), which distinguish polyethylene resins. Chain branches also become points in the molecular network where oxidation may take place. (Wan et al. , 2006)
2.5
Mechanical Milling Method
Two different terms are commonly used in the literature to denote the processing of powder particles in high-energy ball mills. Mechanical Alloying (MA) describes the process when mixtures of powders (of different metals or alloys/compounds) are milled together. Material transfer is involved in this process to obtain a homogeneous alloy. On the other hand, milling of uniform (often stoichiometric) composition powders, such as pure metals, intermetallics, or prealloyed powders, where material transfer is not required for homogenization, has been termed Mechanical Milling (MM). The destruction of long-range order in intermetallics to produce either a disordered intermetallic or an amorphous phase has been referred to as Mechanical Disordering (MD). The advantage of MM/MD over MA is that since the powders are already alloyed and only a reduction in particle size and/or other transformations need to be induced mechanically, the time required for processing is short. For example, MM requires half the time required for MA to achieve the same effect. Additionally, MM of powders reduces oxidation of the constituent powders, related to the shortened
Chapter 3
METHODOLOGY
3.1
Location of research
The research will be conducted at Laboratory of Basic Physics (MFA) in Department of Physical Sciences, Faculty of Science and Technology, University Malaysia Terengganu (UMT).
3.2.2
Characterization
Every 20 hours alternate of ball milling, little grain size of powder will be taken out and do the characterization by using the X-ray diffraction (XRD) to determine the crystalline size and using the Scanning electron microscope (SEM) to determine the graphite morphology.
3.2.3
Compounding process (composite)
In this process, MDPE will mix with the graphite by using the HAAKE Polylab system. The blending process will carry out 5 samples; each sample will use 0wt%, 1wt %, 2wt%, 3wt%, 4wt% mix with the MDPE. The materials were compounded into different mixture ratios of graphite content in MDPE. The MDPE will compound at 180℃ and 170RPM for 20 min. Firstly, the MDPE will add to the mixer until the MDPE fully melt and be liquid, and then the graphite powder is added until the mixing torque become stabilized.
3.2.5 Analysis
Lastly, MDPE-graphite composite be produced. Testing and analysis were perform on this stage. Table below shows several characterizations method and description in this research.
Table3.1 : Instruments and method Method
Description
Thermogravimetry (TGA)
Determine change of weight in relation of the change of temperature
X-ray diffraction (XRD)
Investigation of the fine structure of matter
Fourier Transform Infrared
Determine the type of bonds which are
Spectroscopy (FTIR)
present in a compound
Testometric MODEL 350/500
Tensile test
Four Point Probe
Determine the conductivity
ML =
m s − mf ms
× 100%
(3.1)
TGA measurements were carried out in a TGA 6 Perkin-Elmer analyzer under a nitrogen atmosphere. Around 10 mg of sample was used. The measurements were performed from 50-800°C at a heating rate of 10°C/ min. (Kosuri et al. , 2008)
3.3.2
X-Ray Diffraction
X-ray diffraction is a tool for the investigation of the fine structure of matter. This technique had its beginnings in von Laue’s discovery in 1912 that crystals diffract Xrays, the manner of the diffraction revealing the structure of the crystal. At first, xray diffraction was used only for the determination of the crystal structure. Later on, however, other uses were developed and today the method is applied not only to structure determination but to such diverse problems as chemical analysis and stress measurement, to the study of phase equilibria and the measurement of particle size, to the determination of the orientation of one crystal or the ensemble of orientations in polycrystalline aggregate.
Bragg’s law states the essential condition which must be met if diffraction is to occur. N is called the order of reflection, it may take on any integral value consistent with sinθ not exceeding unity and is equal to the number of wavelengths in the path difference between rays scattered by adjacent planes. Therefore, for fixed values of λ and d, there may be several angles of incidence θ1, θ2, θ3 … at which the diffraction may occur corresponding to n=1,2,3… Debye Scherrer’s formula is used to calculate the crystallite lamella size. Scherrer’s equation is given as Crystallite Lamella size= 0.9 λ/(B cos θ) Where, B is full width half maxima in nm. (Kosuri et al. ,2008)
3.3.3
Fourier Transform Infrared Spectroscopy (FTIR)
Fourier transform infrared spectroscopy is another form of infrared spectroscopy which does not bombard the samples using infrared radiation of individual wavelengths. Instead, FTIR uses sends out a pulse of beam which contains the information of all infrared wavelengths. The beam is transmitted through the sample,
3.3.4
Testometric Model 350/500
Testometric Model 350/500 design and manufacture a comprehensive range of materials testing machines and software for evaluating the mechanical properties and performance of materials. It has two type of this model, there are AT range of standalone universal strength testing machines and the CT range of universal strength testing machines. Testometric machine can done the testing including tensile test, wet strength and puncture of tissue, board tests include flat, ring edge and the etc. Accessories for paper testing include a wide range of grips and fixtures for paper testing and all are compliant to international standards.
3.3.5
Four Point Probe
Four point probes method is a simple apparatus for measuring the resistivity of semiconductor samples. By passing a current through two outer probes and measuring the voltage through the inner probes allows the measurement of the substrate
3.4
Process Flow Chart
Preparation of samples-mill graphite (20, 40, 60, 80,100 hr)
Characterization graphite
XRD SEM
Compounding process
MDPE
MDPE
MDPE
MDPE
MDPE
+
+
+
+
1wt%
2wt%
3wt%
4wt%
graphite
graphite
graphite
graphite
Chapter 4
EXPECTED RESULTS
Graphite transforms to an amorphous phase by ball milling, the average size reach from 3nm to 8nm after 60 hour milling.
When MDPE mix with the graphite, crystallinity will increase and structure will be more close packing. When crystallinity increases, hardness will increase. Tensile
REFERENCES
Peres, M. F. , Schön, C.G. & Tarpani, J.R. 2010 Effect of precracking method on KIc results for medium-density polyethylene tested under cryogenic condition. Journal of Polymer Testing 29 : 667 – 673 Brown, N. Intrinsic lifetime of polyethylene pipelines. 2007. Polymer Engineering and Science. doi:10.1002/pen :477 – 480 Mohammad Shishesaz1 & Mohammad Reza Shishesaz . 2008. Applicability of Medium Density Polyethylene Gas Pipes in Hot Climate Areas of South-west Iran. Iranian Polymer Journal. 17 (7), 503-517 Zhang , W. , Dehghani-Sanij , A. A. & Blackburn, R.S. 2007 Carbon based conductive polymer composites. J Mater Sci. 42: 3408 3418
Wolak, J. E. 2005. Polyolefin miscibility: Solid-state NMR investigation of phase behavior in saturated hydrocarbon blends. Dissertation Degree of Doctor of Philosophy. North Carolina State University. Dhoot, S.N. , B.S. & M.S. 2004. Sorption And Transport Of Gases And Organic Vapors In Poly(Ethylene Terephthalate). Dissertation Degree of Doctor of Philosophy. University of Texas, Austin. Suryanarayana, C . 2001. Mechanical alloying and milling. Journal of Progress in Materials Science, 46: 1-184 Wan Aizan & Rahman, W.A. 2006. Design of silane crosslinkable high density polyethylene compounds for automotive fuel tank application. Thesis of project IRPA. Faculty of Chemical and Natural Resource Engineering, Universiti Teknologi Malaysia
APPENDIX
Table A1: commercially produced metallocenes
Table A2: Gantt Chart for FYP
Month No.
Task
2010 JUL
1
Literature Review
2
Title Selection & Submission
3
Writing Proposal
4
Proposal Submission
5
Proposal Presentation
6
Lab work 1 (Preparation)
7
Lab work 2 (Compounding)
8
Writing Progress Report 1
9
Writing Progress Report 2
10
Thesis Writing
11
Submit Final Draft
12
Final Presentation
13
Thesis Submission
AUG
20
SEP
OCT
2011 NOV
DEC
JAN
FEB
MAR
APR
