Polymer Properties :Experiment 1 Tensile Test

Polymer Properties (EBT 326)

Exp. 1 : Tensile Test

EXPERIMENT 1 Tensil Te nsilee Te Test st

1.0 OBJECT OBJECTIVE IVE 1.1 To emphasis the use of tensile using Instron mahine to the polymer materials. materials. 2.0 INTROD INTRODUCT UCTION ION

The mehanial properties of materials are !etermine! "y performing arefully !esigne! la"oratory experiments that repliate as nearly as possi"le the ser#ie on!itions. In real life$ there are many fators in#ol#e! in the nature in %hih loa!s are applie! on a material. The follo%ing are some ommon examples of mo!es in %hih loa!s might "e applie!: tensile$ ompressi#e$ an! shear. These properties are important in materials seletions for mehanial !esign. &ther fators that often ompliate the !esign proess inlu!e temperature an! time fators. The topi of this la" is onfine! to the tensile property of polymers. 'igure 1 sho%s a tensile testing mahine Instron mahine. This test is a !estruti#e metho!$ in %hih a speimen of a stan!ar! shape an! !imensions (prepare! aor!ing to ASTM to ASTM D 638: 638: stan!ar! test metho! for tensile properties of plastis) is su"ete! to an axial loa!. Tensile testing is the measurement of the a"ility of a material to o#erome fores pulling the sample apart an! the extent it strethes "efore "rea*ing. Tension Tension test is another name of tensile test. It is material siene test %hih a speimen is su"ete! to the stress until it "rea*s. +uring a typial tensile test$ a !um""ell ! um""ell shape! speimen is grippe! at its t%o en!s an! is pulle! to elongate at a !etermine! rate to its "rea*point a highly !utile polymer may not reah its "rea*point. The tensile tester use! in this la" is manufature! "y Instron mahine. The setup of the experiment oul! "e hange! to aommo aommo!at !atee !iffer !ifferent ent types types of mehani mehanial al testi testing$ ng$ aor!i aor!ing ng to the ,-T ,-T stan!ar stan!ar! ! (e.g. (e.g. ompression test$ et).

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'rom 'rom the the tens tensil ilee test test resu result lt$$ the the mo!u mo!ulu luss of elas elasti tii ity ty$$ elas elasti ti limi limit$ t$ elong elongat atio ion$ n$ proportional limit$ re!ution in area$ tensile strength$ yiel! point$ yiel! strength$ strain rate$ stress rate an! other tensile properties are o"taine!. ,ll of this tensile properties$ %e an measure! an! o"tain it from the loa! #ersus elongation ur#e %hih is then on#erte! into a stress #ersus strain graph %hih pro!ue! "y the tensile test mahine.

'igure 1 : -tress strain ur#e for polymer materials /eferring to typial stress0strain ur#e of polymer materials as$ the tensile properties !efine! as follo%s: •

Tensile stress  the fore applie! to pro!ue !eformation in a unit area of a speimen. It expresse! in fore per unit area. stress

E

strain

σ



ε

•

Tensil Tensilee strength strength  maximum tensile tensile stress stress supporte! supporte! "y speimen speimen !uring !uring test an! also

•

!esri"es the stress to "rea* the sample. Tensile Tensile strength at "rea*  tensile strength at the mo ment of rupture of the sample. -tra -train in  the the hang hangee in leng length th per per unit unit of origi origina nall lengt length h (,I (,I). ).It It is expr expres esse se! ! as a

•

!imensionless ratio.

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•

Elongation  the inrease in length of the speimen pro!ue! "y a tensile loa!. 4iel! point  the first point on the stress0strain ur#e at %hih an inrease in strain ours

•

%ithout the inrease in stress. 4iel! strength  the stress at %hih a material exhi"its a speifie! limiting !e#iation from

•

the proportionality of stress to strain. This stress %ill "e at yiel! point. Proportional limit  the greatest stress at %hih a material is apa"le of sustaining the

•

applie! loa! %ithout any !e#iation from proportionality of stress to strain (5oo*es 7a%). o!ulus of elastiity  the ratio of stress to orrespon!ing strain "elo% the proportional

•

limit. 8ltimate strength  the maximum stress a material %ill %ithstan! %hen su"ete! to an

•

• •

applie! loa! in ompression$ tension or shear. 4oungs mo!ulus  initial slope of the stress0strain ur#es. Toughness  the area un!er the stress0strain ur#es. This area has the units of energy per unit #olume an! is the %or* expen!e! in !eforming the materials.

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3.0 COMPONENTS AND EQUIPMENTS 3.1 Instron mahine

'igure 2: Instron mahine 3.2 9ernier aliper

'igure 3: 9ernier aliper 3.3 -amples

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'igure 6: PP (%ith a!!iti#e)


'igure <: 7+PE

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4.0 PROCEDURES .1 The polymer samples %ere inetion0mol!e! into !um""ell shapes. .2 The %i!th$ thi*ness an! gauge length of eah sample %as measure! using #ernier

aliper in mm. These !imensions shoul! "e approximately the sa me for eah sample. .3 The gap "et%een the upper a% an! lo%er a% of the Instron mahine %as a!uste! an! set at 1=m.

'igure >: ?a%s a!uste! to 1=m gap

. The ross hea! spee! of Instron mahine %as set at ;= mmmin. .; The sample 1 %as lippe! tightly in "et%een of the a%s.

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'igure @: sample %as lippe! tightly "et%een a%s

.6 To start up the test$ the start "utton of the Inston mahine %as presse!. The upper a% %as proee!e! to mo#e up%ar!s at the rate set. &ne the failure ourre!$ the results an! stress0stain graph is automatially reor!e!.

'igure 1=: failure ourre!

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.< To allo% upper a% return to its original position$ the return "utton of the Inston mahine %as presse!. .> 'or the next plastis samples$ steps .3 0 .< %ere repeate!. .@ 'or more !etails$ ,-T + 63> (plastis) an! ,-T + 12 (ru""er) %ere referre! .0 RESU!TS AND DISCUSSION Belo% are the graphs for all the experiment using pure Polypropylene (PP) using ; samples:

Ultimate tensile

Yield strength

Breakin g strength

Modulus of elasticity

'igure 11: The stress0strain ur#e of pure PP (sample 1) at ;= mmmin

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Ultimate tensile

Yield strengt h

Modulus of elasticity

Breaking strength point


Ultimate tensile strength

Yield strengt

Breakin stren th Modulus of elasticity


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Ultimate tensile

Yield strengt

Modulus of


'igure 1: The stress0strain ur#e of pure PP (sample ) at ;= mmmin

Ultimate tensile

Yield strengt

Breaking strength point Modulus of

'igure 1;: The stress0strain ur#e of pure PP (sample ;) at ;= mmmin

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Belo% are the graphs for all the experiment using Polystyrene (P-) using  samples (sample 2 %as reete!):

Ultimate tensile

Yield strengt

Breakin g strength

Modulus of

'igure 16: The stress0strain ur#e of P- (sample 1) at ;= mmmin

Ultimate tensile strength Yield strengt


Modulus of

'igure 1<: The stress0strain ur#e of P- (sample 3) at ;= mmmin

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Ultimate tensile strength

Yield strengt

Breakin g strength

Modulus of

'igure 1>: The stress0strain ur#e of P- (sample ) at ;= mmmin

Ultimate tensile

Yield strengt h

Breakin g strength

Modulus of

'igure 1@: The stress0strain ur#e of P- (sample ;) at ;= mmmin

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Belo% are the graphs for all the experiment using 7+PE using  samples:

Ultimate tensile

Yield

Breaking strength

Modulus of

'igure 2=: The stress0strain ur#e of 7+PE (sample 1) at ;= mmmin

Ultimate tensile

Breaking strength

Yield

Modulus of

'igure 21: The stress0strain ur#e of 7+PE (sample 2) at ;= mmmin

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Ultimate tensile

Breaking strength

Yield

Modulus of

'igure 22: The stress0strain ur#e of 7+PE (sample 3) at ;= mmmin

Ultimate tensile

Yield

Breaking strength

Modulus of

'igure 23: The stress0strain ur#e of 7+PE (sample ) at ;= mmmin

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Belo% are the graphs for all the experiment using PP (%ith a!!iti#e: pigment olor filler) using ; samples:

Ultimate tensile

Breaking strength Yield

Modulus of

'igure 2: The stress0strain ur#e of PP %ith a!!iti#e (sample 1) at ;= mmmin

Ultimate tensile

Yield

Breaking strength

Modulus of

'igure 2;: The stress0strain ur#e of PP %ith a!!iti#e (sample 2) at ;= mmmin

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Ultimate tensile Breaking strength Yield

Modulus of

'igure 26: The stress0strain ur#e of PP %ith a!!iti#e (sample 3) at ;= mmmin

Ultimate tensile

Breaking strength

Yield

Modulus of

'igure 2<: The stress0strain ur#e of PP %ith a!!iti#e (sample ) at ;= mmmin

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Ultimate tensile

Breaking strength

Yield

Modulus of

'igure 2>: The stress0strain ur#e of PP %ith a!!iti#e (sample ;) at ;= mmmin

'rom 'igure 11 until 'igure 2> sho%n the stress0ur#e of all the material pure PP$ a!!iti#e PP$ P- an! 7+PE %ere teste! in the experiment using spee! of ;= mmmin fixe!. Those ur#es sho%e! that e#ery material ha! sho%n !ifferent figure ur#es %hih means it #aries on their mehanial properties too. Ta"le 1 gi#e some information a"out four samples "ase! on fe% properties mo!ulus of elastiity$ yiel! stress$ yiel! strain$ stress at "rea*$ strain at "rea* an! ultimate tensile "rea*.

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.1


B"se# $n t%e &'"(% $) st'ess*st'"in +,'-es #ete'/ine "ll t%ese tensile ('$(e'ties "s

/$#,l,s iel# st'ess iel# st'"in st'ess "t 'e" "n# st'"in "t 'e" "'e #ete'/ine#.

Ta"le 1 : The highest measurement of the tensile properties "ase! on stress #ersus strain graph of four polymer at ;= mmmin rate.

o!ulus -peimen

of

4iel! stress

4iel! strain

elastiity

(Pa)

(A)

(PaA)

-tress at

-train at

"rea*

"rea*

(Pa)

(A)

8ltimate tensile strength (Pa)

Pure Polypropylene

2.<

13.;

.;

13.16

112

21.;

1.>13

3.;2

2.3

3.>

3.6>

36.3

=.<<

<.6<

1;.<3

<.@3

@>.<1

>.2

13.6<6

23.

2.3

3=.1

2.>

32.>

(PP) (sample 1) Polystyrene (P-) (sample 3)

7o% +ensity Polyethylene (7+PE) (sample 1) Polypropylene %ith a!!iti#e (PP) (sample ;)

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&# %$ %# 2$

Modulus of elasticity (Mpa')

2#

Yield strength (Mpa)

he "alue of

Ultimate tensile strength (Mpa)

1$ 1# $ # PP (pure)

PS

LP!

PP (additi"e)

'igure 2@: The hart of four tensile tests

/efer to the hart a"o#e$ there are three properties of !ata that gaine! from the tensile test are plotte! into the hart$ %hih are mo!ulus of elastiity$ yiel! strength an! ultimate tensile strength. Eah properties are teste! using four !ifferent samples %hih are 7o% +ensity Polyethylene (7+PE)$ pure Polypropylene (PP)$ Polypropylene (PP) %ith a!!iti#e an! Polystyrene (P-). o!ulus of elastiity !esri"e! tensile elastiity the ten!eny of an o"et or sample to !eform along an axis %hen opposing fore are applie! along that axis. It also !efine! as a measure of the a"ility of a material to %ithstan! hanges in length %hen un!er length%ise tension or ompression "efore the yiel! point %hih the material an return "a* to its original shape. The highest #alue "et%een the four samples is Polypropylene (PP) %ith a!!iti#e %ith 1 paA$ after that pure Polypropylene (PP) %ith 2.< paA$ Polystyrene (P-) %ith 1.> paA an! lastly 7o% +ensity Polyethylene (7+PE) %ith =.<< paA. 'rom the result %e an see that the is Polypropylene (PP) %ith a!!iti#e is the material that an %ithstan! the hanges happen to it #ery %ell ompare to others sample. 4iel! strength refers to an in!iation of maximum stress that an "e !e#elope! in a material %ithout ausing plasti !eformation. It is the stress at %hih a material exhi"its a

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speifie! permanent !eformation an! is a pratial approximation of the elasti limit. The sample that has highest yiel! strength is Polystyrene (P-) %ith 3.; Pa an! the lo%est yiel! strength #alue o"taine! is <.6< Pa %hih is "elongs to 7o% +ensity Polyethylene (7+PE). 7ast properties that has "een #alue! is ultimate tensile strength %hih refer to the maximum stress that a material an %ithstan! %hile "eing streth or pull$ in this experiment$ "y using Instron mahine$ "efore it failing or "rea*ing. 'rom the experiment$ it has "een pro#e! that Polystyrene (P-) has the highest ultimate tensile strength "efore it "ro*e %hen it "een strethe! %ith #alue of 36.3 Pa. The material that has lo%est ultimate tensile strength is 7o% +ensity Polyethylene (7+PE) %ith >.2 Pa. .2 Me"s,'e "'e" ,n#e' t%e st'ess -e's,s st'"in +,'-e ,sin& Pl"'i/ete' $' $t%e' /et%$#s %"t is t%e /e"nin& $) t%is "'e"

hen a graph of stress0strain ur#e is plotte!$ the area un!er the graph is eCual to the toughness of the material teste!.

'igure 3=: ,rea un!er graph of stress0strain ur#e

The area un!er the graph an "e o"taine! from the formula: 8  ( E D / 2 )  2 !* modulus of elasticity (MPa' ) 2 ε+

* strain at ,reak

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.3 Dis+,ss $n #i))e'en+es $) st'ess*st'"in ('$(e'ties 5)i&,'e6 )$' #i))e'ent t(e $) s"/(les. 7$8 t%e'/"l %ist$' +"n "))e+t /i+'$st',+t,'e "n# /e+%"ni+"l e%"-i$' $) se/i*+'st"lline /"te'i"ls 

E#ery material that has "een teste! in this experiment has their o%n properties strutural properties an! mehanial properties. +ue the #aries of the properties$ e#ery materials %ill #aries its o%n stress0strain ur#e graph as long as its properties. Polystyrene is a glassy$ "rittle polymer %ith lo% toughness an! a softening temperature of only 1==FG. Its a!#antage o#er other polymers is the ease %ith %hih it an "e proesse! "y extrusion$ inetion an! #auum forming. Polypropylene has higher strength an! stiffness than polyethylene an! "etter heat resistane (melting temperature approx. 16=FG) so it an "e use! in appliations %here ontat %ith hot %ater an! steam may "e in#ol#e!. In this experiment %e use! t%o types of polypropylene %hih is pure an! other one ha#e a!!iti#e a!!e!. , pigment olor filler a!!e! thus ma*e the other PP is in "la* olor ompare! to the yello%ish olor. The !isa!#antages of polypropylene are its loss of flexi"ility at temperatures "elo% =FG an! it is more permea"le to gases than is high !ensity polyethylene !ue to its lo%er !egree of rystallinity. The lo% !ensity polyethylene (7+PE) has "ranhe! polymer hains an! therefore the struture of this gra!e of polyethylene is largely amorphous. It has a !ensity of approximately =.@2 an! a melting temperature of 11;FG. The merits of the polymer are its lo% ost$ flexi"ility at temperatures !o%n to 12=FG$ high toughness an! hemial inertness to a %i!e range of liCui!s an! soli!s. The effet on thermal history are #ery important on polymer shoul! "e stu!ie! in !etail as the !egree of rystallinity reahe! "y polymers !epen!s on thi! history. This rystallinity !egree in turn go#erns the "eha#iour of mehanial properties suh as rigi!ity an! resistane. It all "eause %hen the thermoplasti is "een synthesiHe it must "e su"mitte! to a transformation proess to o"tain finishe! pro!ut. This proess inlu!e !ifferent #aria"le %hih influene the final harateriHations of the pro!ut. The most important of them are thermal history gi#en to the polymer !uring the soli!ifiation proess an! moleular %eight.

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hen the thermoplasti polymer ha! "een !one synthesiHe!$ the thermoplasti must "e su"mitte! to a transformation proess to !etermine the en! result of the pro!ut. This proess inlu!e !ifferent #aria"le$ %hih influenes the result of the pro!uts$ %hih the most important of them is the thermal history gi#en to the polymer !uring the soli!ifiation proess an! moleular %eight. -ine the !egree of rystanility reahe! "y these polymers %hih is also !epen! on this history$ this rystanility in turns go#erns the mehanial "eha#ior of properties suh as tenaity$ resistane an! rigi!ity . hen semi0rystalline polymers are use! in manufaturing$ proess of finishe! pro!uts$ heat transfer %ill ta*e plaes %hen it is un!ergoes soli!ifiation. GonseCuently$ non0uniform rystallinity profiles an "e pro!ue! in material or more than one physial rystalline struture an "e !e#elope! on the %alls of the plasti pro!uts manufature!. Thus the !e#elopment of the suita"le metho! to harateriHe! an! analyHe the influenes of thermal history gi#en to a plasti pro!ut$ onsisting of semi0rystalline polymers at the time its manufature! %ill help to optimiHe proessing yles an! !esign a proper ontrol of the thermal parameters in#ol#e!.

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9.0 CONC!USION

,s the onlusion$ from this experiment$ the o"eti#e %hih is to emphasis the use of tensile using Instron ahine to the polymer materials is suessfully ahie#e!. e ha! impro#e! the *no%le!ge of han!ling Instron mahine an! its soft%are %hih is #ery useful espeially to sur#i#e in the material engineering fiel!. Besi!es that$ %e also ha#e learnt on ho% to rea! the stress0strain graph an! interpret all the information that gi#en graph.

:.0 RE;ERENCES

1J

. '. -mith an! ?. 5ashemi. Foundation of Materials Science and Engineering, ;th. e!.

Ke% 4or*: The Lra%05ill Gompanies$ In$ 2=11$ pp. 23=023; 2J

rs ,nis -ofia -ufian an! +r oh! 'ir!aus &mar$ Laboratory Manual for Polymer

Proerties$ 8ni#ersiti alaysia Perlis$ Perlis$ 2=1. 7eturesJ. ,#aila"le: 8ni,P Portal$ http:portal.unimap.e!u.my aesse! on @ -ept. 2=1;J. 3J

.+. Gallister$ Fundamental of materials science and engineering!an interacti"e e#

te$t $2==1$ ?ohn illey M -ons$ In.$ Ke% 4or*$ I-BK =0<103@;;10x.

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Polymer Properties :Experiment 1 Tensile Test

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