Aa-Polymer Technology 1(2)

7/26/2019 Aa-Polymer Technology 1(2)

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POLYMER TECHNOLOGYHikmat S Al Salim


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MATERIALS TO BE COVERED EP425 Introductionto Polymers:

Introduction, classifcation o polymers, chemical nature o polymers, polymer st

(amorphous and crystalline), molecular weight o polymers.

Polymerization Mechanisms:

Step growth, chain-growth, condensation, ree radical, ionic, coordination, polym

group transer

Polymerization Systems:

"ulk, solution, suspension, emulsion, gas-phase. Molecular Weight of Polymers

$ethods o measurement o molecular weight.

Additives, Blends & Comosites:

%lasticiers, fllers and reinorcements& polymer

!lends& mechanical properties o composites, composite a!rication.

$ay -Aug%olymer %roduction


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INTRODUCTION TO POLYMERS

%olymers are also called macromolecules due to their large sie !

con+erse is not always true. A macromolecule mayor may not con

monomer units, e.g., chlorophyll (H'/01$g) is a macromo

!ut not a polymer since there are no monomer units present so w

conclude that all polymers are macromolecules while all macromo

may not !e polymers in nature.

2he terms polymer and monomer were deri+ed rom the 3reek ro

(many), mono (one) and meros (part).

%olymers are materials composed o long molecular chains that a

accepted or a wide +ariety o applications. 2his unit e4plores the

materials in terms o their chemical composition, associated prop

and processes o manuacture rom petrochemicals. 2he unit also

range o products in which polymers are used and e4plains why tchosen in preerence to many con+entional materials.



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GROWTH AND USES OF POLYMERS



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POLYMER TYPES

. 2raditionally, the industry has produced two main types o synthet

6 plastics and ru!!ers.

'. 2he distinction is that plastics are, !y and large, rigid materials at s

temperatures while ru!!ers are 7e4i!le, low modulus materials whlong-range elasticity.

5. %lastics are urther su!di+ided into thermoplastics and thermosets

type !eing materials where the long chains are linked together !y

a eature they share with con+entional +ulcanied ru!!ers.

1. 2he distinction in terms o sti8ness has !ecome !lurred !y the de+

o thermoplastic elastomers (2%9s). $oreo+er, all polymers, irrespetheir nature, can !e reinorced !y a +ery wide range o fllers to pro

composite materials.



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CLASSIFICATION OF POLYMER BYPROPERTY



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CLASSIFYING OF POLYMERS BY DESIGNFUNCTION



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SEQUENCE OF USE OF POLYMERS

. ;ood rom +arious species o tree, f!res or rope and te4t

'. Am!er adhesi+e or attaching stone and metal tools to wohandles.

5.


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*. 2he true molecular nature o materials like naturubberand synthetics like Bakelite was notunderstood until a!out the >'s 2hat period sagrowth o polymer chemistry, !y which monom!e synthesised and polymeried in a controlled gi+e macromolecular materials.

. Some o today?s ma@or polymers were disco+ere

period and were commercialised in the >5s a>1s. 2hey included materials like polychlorop(Neopreneru!!er), nylon, polyester(Teryleneor Dacron) and polyethylene (Polyth



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MONOMER SOURCES IN EARLY DA

. irst !een !ased on coal tar deri+ati+es !ut, with the rise petrochemical industry !ased on oil and natural gas, a muwider range o !asic chemical !uilding !locks !ecame a+a

'. All chemical con+ersions in oilB gas industryproduce somunsaturated compounds. Some more than others such thermal cracking in the a!sence o hydrogen and at highpressure.

5. 0o+el polymers, like aromaticpolyamides andpolyimidwhich were disco+ered only in the >*s, ha+e !een de+ewhile speciality, high temperature materials like

polysulphonesha+e penetrated new markets hithertoinaccessi!le to the traditional range o commercial polym



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WRITING FORMULAS FOR POLYMERICMACROMOLECULES

2he repeating structural unit o most simple polymers no

re7ects the monomer(s)rom which the polymers are con

!ut also pro+ides a concise means or drawing structures tothese macromolecules.

or polyethylene, here ethylene (ethene) is the monomer,

corresponding linear polymer is called high-density polyeth

(HC%9).

2his polymer is called polyethylene rather than polymethyl

H'-)n, !ecause ethylene is a sta!le compound !methyle

and it also ser+es as the synthetic precursor o the polyme



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Dnlike simpler pure compounds, most polymers are not co

identical molecules. 2he HC%9 molecules, or e4ample, are

car!on chains, !ut the lengths may +ary !y thousands o m

units

"ecause o this,polymer molecular weights are usually

a+erages. 2wo e4perimentally determined +alues are comm

Mn , the num!er a+erage molecular weight, is calculatmole raction distri!ution o di8erent sied molecules in

and Mw, the weight a+erage molecular weight, is calcuthe weight raction distri!utiono di8erent sied molec



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is necessarily skewed to higher +alues, and is a

greater than . As the weight dispersion o molec

a sample narrows, approaches , and in the unli

case that all the polymer molecules ha+e identic

weights (a pure mono-disperse sample), the rat

!ecomes unity


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Name(s) Formula Monomer Properties

Polyethylene

low density (LDPE)(CH2CH2)n

ethylene

CH2!CH2so"t# wa$y solid

Polyethylene

hi'h density (HDPE)(CH2CH2)n

ethylene

CH2!CH2ri'id# translu%ent solid

Polypropylene

(PP) di""erent 'radesCH2CH(CH)*n

propylene

CH2!CHCH

ata%ti%+ so"t# elasti% solid

isota%ti%+ hard# stron' solid

Poly(,inyl %hloride)

(P-C) (CH2CHCl)n

,inyl %hloride

CH2!CHCl stron' ri'id solid

Poly(,inylidene %hloride)

(.aran /)(CH2CCl2)n

,inylidene %hloride

CH2!CCl2dense# hi'hmeltin' solid

Polystyrene

(P.)CH2CH(C0H1)*n

styrene

CH2!CHC0H1

hard# ri'id# %lear solid

solu&le in or'ani% sol,ents

Polya%rylonitrile

(P/N# 3rlon# /%rilan)(CH2CHCN)n

a%rylonitrile

CH2!CHCN

hi'hmeltin' solid

solu&le in or'ani% sol,ents

Polytetra"luoroethylene

(P4FE# 4e"lon)(CF2CF2)n

tetra"luoroethylene

CF2!CF2resistant# smooth solid

Poly(methyl metha%rylate)

(PMM/# Lu%ite# Ple$i'las)CH2C(CH)C32CH*n

methyl metha%rylate

CH2!C(CH)C32CHhard# transparent solid

Poly(,inyl a%etate)

(P-/%)(CH2CH3C3CH)n

,inyl a%etate

CH2!CH3C3CHso"t# sti%y solid

%isPolyisoprene

natural ru&&erCH2CH!C(CH)CH2*n

isoprene

CH2!CHC(CH)!CH2so"t# sti%y solid

Poly%hloroprene (%is 7 trans)

(Neoprene)CH2CH!CClCH2*n

%hloroprene

CH2!CHCCl!CH2tou'h# ru&&ery solid


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PROPERTIES OF MACROMOLECULES

#$P%is a rigid translucent solidwhich sotens on heating

a!o+e 100 !, and can !e ashioned into +arious orms including

flms. It is not as easily stretched and deormed as is FC%9. #$P%

is insoluble in water and most organic sol"ents, although

some swelling may occur on immersion in the latter. HC%9 is an

e4cellent electrical insulator.

$P%is a so#t translucent solid which deorms !adly a!o+e

$% !. ilms made rom FC%9 stretch easily and are commonlyused or wrapping& 'DP is insoluble in water but so#tens

and swells on e*posure to hydrocarbon sol"ents. "oth FC%9

and HC%9 !ecome !rittle at +ery low temperatures (!elow -:G

).$ay -Aug%olymer %roduction


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Natural (late*) rubberis an opaue, sot, easily deorm

solid that !ecomes sticky when heated !a'ove( )*+ C), a

!rittle when cooled 'elo -.*+ C(It swells to more than

its sie in nonpolar organic sol"ents like toluene, e+edissol+ing, !ut is impermea!le to water. 2he !%,-monom

isopreneis a +olatile liuid (!.p. 51G ).

Pure cellulose, in the form of cotton, is a sot 7e4i!le

essentially unchanged !y +ariations in temperature rangi

- to :G . otton a!sor!s water readily, !ut is una8ec

immersion in toluene or most other organic sol+ents. !el

.bers may be bent and twisted but do not stretch

be#ore breaking&2he monomer o cellulose is the

!/

,1

/

aldohe*ose C-glucose. 3lucose is a water solu!$ay -Aug%olymer %roduction


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WHAT IS A COPOLYMER ? NOMENCLATURES

Coolymers are olymers o'tained 'y olymerization of to o

di0erent monomers(



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PROPERTIES OF MACROMOLECULESMorhology

. "ecause polymer molecules are so large, they generally pack toge

uniorm ashion, with ordered or crystalline-likeregions mi4ed togedisordered or amorphous domains

'. rystallinity occurs when linear polymer chains are structurally oriuniorm three-dimensional matri4

5. Increased crystallinity is associated with an increase in rigidity, tenand opacity(due to light scattering).

1. Amorphous polymers are usually less rigid, weaker and more

easily deormed. 2hey are oten transparent



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THREE FACTORSTHAT INFLUENCE DEGREE OFCRYSTALLINITYARE

i" hain length

ii" hain !ranching

iii" Interchain !onding

2o illustrate the e8ects and di8erences !etween i" and ii" considerE

HC%9 is composed o +ery long un!ranched hydrocar!on chains. 2hese pack t

in crystalline domains that alternate with amorphous segments, and the result

while relati+ely strong and sti8, retains a degree o 7e4i!ility. In contrast, FC%9

o smaller and more highly !ranched chains which do not easily adopt crystall

2his material is thereore soter, weaker, less dense and more easily deormed

2he e8ects o iii" (see ne4t slide.) ellulose is the perect e4ampleE



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cellulose chains easily adopt a sta!le rod-like conormation. 2hese m

align themsel+es side !y side into f!ers that are sta!ilied !y inter-c

hydrogen !onding !etween the three hydro4yl groups on each mono

unit. onseuently, crystallinity is high and the cellulose molecules dmo+e or slip relati+e to each other. 2he high concentration o hydro4

groups also accounts or the acile a!sorption o water that is charac

o cotton.

0atural ru!!er is a completely amorphous polymer.

Dnortunately, the potentially useul propertieso raw late4 ru!!er are limited !y temperature

dependence& howe+er, these properties can !e

modifed !y chemical change.!vulcanization"



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VULCANIZATION - CHARLES GOODYEAR IN 1839

I instead, the chains o ru!!er molecules are slightly cross-linked !y

atoms, a process called vulcanizationthe desira!le elastomeric pro

ru!!er are su!stantially impro+ed. At ' to 5 crosslinking a useul so

that no longer su8ers stickiness and !rittleness pro!lems on heating

cooling, is o!tained. At ' to 5 crosslinking a rigid hard ru!!er pro

ormed.



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/n heating or cooling most polymers undergo thermal

transitions thatpro"ide insight into their morphology.

2hese are defned as the melt transition, 1m, and the glass

transition, 1g

1mis the temperature at which crystalline domains lose their

structure, or melt. As crystallinity increases, so does 2m.

1gis the temperature !elow which amorphous domains lose the

structural mo!ility o the polymer chains and !ecome rigid

glasses.


Polymer LDPE HDPE PP P-C P. P/N P4FE PMM/ 8u&&

4m(9C) ::; :; :


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WHAT IS GLASS TRANSITION TEMPERATUROF A POLYMER? AND WHAT SHOULD I KN

ABOUT IT?

. 2he glass transition temperature is a unction o chain2e*ibility. 2he glass transition occurs when there is enough+i!rational (thermal) energy in the system to create suJcient ree-+olume to permit seuences o *- main-chain car!ons to mo+etogether as a unit. At this point, the mechanical !eha+iour o thepolymer changes rom rigid and !rittle to tough and leathery --- the!eha+iour we defne as plastic !eha+iour.

'. 2here is no relationship !etween the glass transition point andcrystalline melt point or a gi+en polymer.



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2( 1gis a unction o the mo!ility o the polymer cwhile 1mis a unction o intermolecular interactrepeat unit stereo regularity.

1. As or crystallinity, it does strengthen the polymat the same time makes it more !rittle.

. In any crystalline su!stance, a orce applied in tdirection o a lattice can produce a micro crack& an amorphous polymer, there is no lattice or a

propagate. 2he !est way to study these e8ects Cynamic $echanical Analysis (C$A).

Aa-Polymer Technology 1(2)

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