Polymer Properties :Experiment 1 Tensile Test

8/19/2019 Polymer Properties :Experiment 1 Tensile Test

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Polymer Properties (EBT 326) Exp. 1 : Tensile Test

EXPERIMENT 1

Tensile Test

1.0 OBJECTIVE

1.1 To emphasis the use of tensile using Instron mahine to the polymer materials.

2.0 INTRODUCTION

The mehanial properties of materials are !etermine! "y performing arefully !esigne!

la"oratory experiments that repliate as nearly as possi"le the ser#ie on!itions. In real life$there are many fators in#ol#e! in the nature in %hih loa!s are applie! on a material. The

follo%ing are some ommon examples of mo!es in %hih loa!s might "e applie!: tensile$

ompressi#e$ an! shear. These properties are important in materials seletions for mehanial

!esign. &ther fators that often ompliate the !esign proess inlu!e temperature an! time

fators.

The topi of this la" is onfine! to the tensile property of polymers. 'igure 1 sho%s a

tensile testing mahine Instron mahine. This test is a !estruti#e metho!$ in %hih a speimen

of a stan!ar! shape an! !imensions (prepare! aor!ing to ASTM D 638: stan!ar! test metho!

for tensile properties of plastis) is su"ete! to an axial loa!. Tensile testing is the measurement

of the a"ility of a material to o#erome fores pulling the sample apart an! the extent it strethes

"efore "rea*ing. Tension test is another name of tensile test. It is material siene test %hih a

speimen is su"ete! to the stress until it "rea*s. +uring a typial tensile test$ a !um""ell shape!

speimen is grippe! at its t%o en!s an! is pulle! to elongate at a !etermine! rate to its

"rea*point a highly !utile polymer may not reah its "rea*point. The tensile tester use! in this

la" is manufature! "y Instron mahine. The setup of the experiment oul! "e hange! to

aommo!ate !ifferent types of mehanial testing$ aor!ing to the ,-T stan!ar! (e.g.

ompression test$ et).


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'rom the tensile test result$ the mo!ulus of elastiity$ elasti limit$ elongation$

proportional limit$ re!ution 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 %hih is then on#erte! into a stress #ersus strain

graph %hih pro!ue! "y the tensile test mahine.

'igure 1 : -tress strain ur#e for polymer materials

/eferring to typial stress0strain ur#e of polymer materials as$ the tensile properties !efine! as

follo%s:

• Tensile stress the fore applie! to pro!ue !eformation in a unit area of a speimen. It

expresse! in fore per unit area.

Estress

strain σ

ε

• Tensile strength maximum tensile stress supporte! "y speimen !uring test an! also

!esri"es the stress to "rea* the sample.

• Tensile strength at "rea* tensile strength at the moment of rupture of the sample.

• -train the hange in length per unit of original length (,I).It is expresse! as a

!imensionless ratio.


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• Elongation the inrease in length of the speimen pro!ue! "y a tensile loa!.

• 4iel! point the first point on the stress0strain ur#e at %hih an inrease in strain ours

%ithout the inrease in stress.

• 4iel! strength the stress at %hih a material exhi"its a speifie! limiting !e#iation from

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

applie! loa! %ithout any !e#iation from proportionality of stress to strain (5oo*es 7a%).

• o!ulus of elastiity the ratio of stress to orrespon!ing strain "elo% the proportional

limit.

• 8ltimate strength the maximum stress a material %ill %ithstan! %hen su"ete! to an

applie! loa! in ompression$ tension or shear.

• 4oungs 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 mahine

'igure 2: Instron mahine

3.2 9ernier aliper

'igure 3: 9ernier aliper

3.3 -amples

'igure : PP (pure) 'igure ;: P-


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'igure


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4.0 PROCEDURES

.1 The polymer samples %ere inetion0mol!e! into !um""ell shapes..2 The %i!th$ thi*ness an! gauge length of eah sample %as measure! using #ernier

aliper in mm. These !imensions shoul! "e approximately the same for eah sample..3 The gap "et%een the upper a% an! lo%er a% of the Instron mahine %as a!uste!

an! set at 1=m.

'igure >: ?a%s a!uste! to 1=m gap

. The ross hea! spee! of Instron mahine %as set at ;= mmmin.

.; 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 mahine %as presse!. The upper a%

%as proee!e! to mo#e up%ar!s at the rate set. &ne the failure ourre!$ the results

an! stress0stain graph is automatially reor!e!.

'igure 1=: failure ourre!


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.< To allo% upper a% return to its original position$ the return "utton of the Inston

mahine %as presse!..> 'or the next plastis samples$ steps .3 0 .< %ere repeate!.

.@ 'or more !etails$ ,-T + 63> (plastis) 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:

'igure 11: The stress0strain ur#e of pure PP (sample 1) at ;= mmmin

Modulus of elasticity

Yield strength

Ultimate tensile

Breakin

g

strength


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Ultimate tensile

Yield

strengt

h


Breaking strength

point

Ultimate tensile strength

Yield

strengt


Breakin stren th


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'igure 1: The stress0strain ur#e of pure PP (sample ) at ;= mmmin

'igure 1;: The stress0strain ur#e of pure PP (sample ;) at ;= mmmin

Ultimate tensile

Yield

strengt

Modulus of

Breaking

strength point

Breaking

strength point

Modulus of

Yield

strengt

Ultimate tensile


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Belo% are the graphs for all the experiment using Polystyrene (P-) using samples (sample

2 %as reete!):

'igure 16: The stress0strain ur#e of P- (sample 1) at ;= mmmin

'igure 1


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'igure 1>: The stress0strain ur#e of P- (sample ) at ;= mmmin

'igure 1@: The stress0strain ur#e of P- (sample ;) at ;= mmmin

Ultimate tensile

strength

Yieldstrengt Breakin

g

strength

Modulus

of

Ultimate tensile

Breakin

g

strength

Yieldstrengt

h

Modulus of


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

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

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

Ultimate

tensile

Breaking

strength

Modulus of

Yield

Ultimate

tensile

Breaking

strength

Modulus of

Yield


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

'igure 23: The stress0strain ur#e of 7+PE (sample ) at ;= mmmin

Breaking

strength

Ultimate

tensile

Yield

Modulus of

Ultimate

tensileBreaking

strength

Yield

Modulus of


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

samples:

'igure 2: The stress0strain ur#e of PP %ith a!!iti#e (sample 1) at ;= mmmin

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

Modulus of

Breaking

strength

Yield

Ultimate

tensile

Breaking

strength

Ultimate

tensile

Yield

Modulus of


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

'igure 2


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

'rom 'igure 11 until 'igure 2> sho%n the stress0ur#e of all the material pure PP$

a!!iti#e PP$ P- an! 7+PE %ere teste! in the experiment using spee! of ;= mmmin fixe!. Those

ur#es sho%e! that e#ery material ha! sho%n !ifferent figure ur#es %hih means it #aries on

their mehanial properties too. Ta"le 1 gi#e some information a"out four samples "ase! on fe%

properties mo!ulus of elastiity$ yiel! stress$ yiel! strain$ stress at "rea*$ strain at "rea* an!

ultimate tensile "rea*.

Breaking

strength

Ultimate

tensile

Yield

Modulus of


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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 ;= mmmin rate.

-peimen

o!ulus

of

elastiity

(PaA)

4iel! stress

(Pa)

4iel! strain

(A)

-tress at

"rea*

(Pa)

-train at

"rea*

(A)

8ltimate

tensile

strength

(Pa)

Pure

Polypropylene

(PP) (sample 1)

2.< 13.; .; 13.16 112 21.;

Polystyrene

(P-) (sample 3)1.>13 3.;2 2.3 3.> 3.6> 36.3

7o% +ensity

Polyethylene

(7+PE)

(sample 1)

=.


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PP (pure) PS LP! PP (additi"e)

#

$

1#

1$

2#

2$

%#

%$

Modulus of elasticity (Mpa')

Yield strength (Mpa)

Ultimate tensile strength

(Mpa)

'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$ %hih are mo!ulus of elastiity$ yiel! strength an! ultimate tensile

strength. Eah properties are teste! using four !ifferent samples %hih are 7o% +ensity

Polyethylene (7+PE)$ pure Polypropylene (PP)$ Polypropylene (PP) %ith a!!iti#e an!

Polystyrene (P-).

o!ulus of elastiity !esri"e! tensile elastiity the ten!eny of an o"et or sample to

!eform along an axis %hen opposing fore 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 %hih 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

paA$ after that pure Polypropylene (PP) %ith 2.< paA$ Polystyrene (P-) %ith 1.> paA

an! lastly 7o% +ensity Polyethylene (7+PE) %ith =.


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speifie! permanent !eformation an! is a pratial 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


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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 strutural

properties an! mehanial 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 %hih it an "e proesse! "y

extrusion$ inetion an! #auum forming.

Polypropylene has higher strength an! stiffness than polyethylene an! "etter heat

resistane (melting temperature approx. 16=FG) so it an "e use! in appliations %here ontat

%ith hot %ater an! steam may "e in#ol#e!. In this experiment %e use! t%o types of

polypropylene %hih 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 "ranhe! polymer hains an! therefore the

struture 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! hemial inertness to a %i!e range of liCui!s

an! soli!s.

The effet on thermal history are #ery important on polymer shoul! "e stu!ie! in !etail as

the !egree of rystallinity reahe! "y polymers !epen!s on thi! history. This rystallinity !egree

in turn go#erns the "eha#iour of mehanial properties suh as rigi!ity an! resistane. It all

"eause %hen the thermoplasti is "een synthesiHe it must "e su"mitte! to a transformation

proess to o"tain finishe! pro!ut. This proess inlu!e !ifferent #aria"le %hih influene the

final harateriHations of the pro!ut. The most important of them are thermal history gi#en to

the polymer !uring the soli!ifiation proess an! moleular %eight.


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hen the thermoplasti polymer ha! "een !one synthesiHe!$ the thermoplasti must "e

su"mitte! to a transformation proess to !etermine the en! result of the pro!ut. This proess

inlu!e !ifferent #aria"le$ %hih influenes the result of the pro!uts$ %hih the most important

of them is the thermal history gi#en to the polymer !uring the soli!ifiation proess an!

moleular %eight. -ine the !egree of rystanility reahe! "y these polymers %hih is also

!epen! on this history$ this rystanility in turns go#erns the mehanial "eha#ior of properties

suh as tenaity$ resistane an! rigi!ity .

hen semi0rystalline polymers are use! in manufaturing$ proess of finishe! pro!uts$

heat transfer %ill ta*e plaes %hen it is un!ergoes soli!ifiation. GonseCuently$ non0uniform

rystallinity profiles an "e pro!ue! in material or more than one physial rystalline struture

an "e !e#elope! on the %alls of the plasti pro!uts manufature!.

Thus the !e#elopment of the suita"le metho! to harateriHe! an! analyHe the influenes

of thermal history gi#en to a plasti pro!ut$ onsisting of semi0rystalline polymers at the time

its manufature! %ill help to optimiHe proessing yles an! !esign a proper ontrol of the

thermal parameters in#ol#e!.


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9.0 CONC!USION

,s the onlusion$ from this experiment$ the o"eti#e %hih is to emphasis the use of tensile

using Instron ahine to the polymer materials is suessfully ahie#e!. e ha! impro#e! the

*no%le!ge of han!ling Instron mahine an! its soft%are %hih is #ery useful espeially 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

Proerties$ 8ni#ersiti alaysia Perlis$ Perlis$ 2=1. 7eturesJ. ,#aila"le: 8ni,P Portal$

http:portal.unimap.e!u.my aesse! 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

Polymer Properties :Experiment 1 Tensile Test

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