chapter 13 introduction to polymer

8/12/2019 Chapter 13 Introduction to Polymer

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CHAPTER 13

INTRODUCTION TOPOLYMER


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At the end of this lecture,students should be able to

Determine types of polymer

Determine physical properties of polymer

Determine types of polymerization


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INTRODUCTION

Pol!"er is a macro"oleculeco"#rised of re#eatin$ structuralunits %oined b! co&alent bonds'

(ree) *ord +#ol!-+"an!, +"er-#arts

The re#eatin$ unit is a $rou# ofato"s co&alentl! bonded to$ether ina s#eci.c s#atial arran$e"ent'

Mono"er the buildin$ bloc) orstructural unit of the #ol!"er'


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/0'/ POLYMERIC MATERIAL1

PolymerInorganic Organic

Natural Synthetic Natural Synthetic

clays(bricks,

cement,

pottery)

sands(glass)

fibres polysaccharides

(starch,

cellulose)

proteins(collagen,

lignins)polyisoprene

(rubbers)

adhesiv

esfibres

coatingsplasticsrubbersresins


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Pol!"ers are usuall! di&ided into t*o$rou#s accordin$ to their #h!sical orche"ical hardenin$ #rocessesther"o#lastic and ther"osettin$ resins'

Ther"o#lastic solid "aterials are#roduced b! si"#l! coolin$ a #ol!"er "elt2#h!sical #rocess3'

e'$' #ol!st!rene, #ol!eth!lene

Ther"oset #roduced b! crosslin)in$reaction 2che"ical #rocess3 bet*een#ol!"er "olecules'

e'$' e#o4ies, #henol resins


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Thermoplastics Thermosets

5i$h "olar "ass "olecules Lo* "olar "ass "olecules

No crosslin)in$ Crosslin)ed

1often u#on heatin$ Deco"#ose che"icall! u#on

heatin$

Can be re"elted Cannot re"elt

Rec!clable Non rec!clable


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POLYMER NAME

P6C Pol!2&in!l chloride3

P1 Pol!2st!rene3

17R 1t!rene8butadiene8rubber

PET Pol!2eth!lene tere#hthalate3

P6A Pol!2&in!l acetate3

PAN Pol!2acr!lonitrile3

1AN 1t!rene8acr!lonitrile co#ol!"er

A71 Acr!lonitrile8butadiene8st!rene ter#ol!"er


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/0'0 CLA11I9ICATION

Pol!"ers can be classi.ed as

Addition #ol!"ers

Condensation #ol!"ers

5o*e&er, so"e #ol!"ers are neithercondensation nor addition #ol!"ers'

Therefore, #ol!"ers are classi.ed based

on the #ol!"erisation "echanis" Chain reaction

1te# reaction


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Addition polymerisation

se:uential addition of onebifunctional;#ol!functional "ono"erto $ro*in$ #ol!"er chains *ithoutthe eli"ination of an! #art of the

"ono"er "olecule'

Pn < M Pn


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Condensation polymerisation

#ol!"ers for"ed fro" bifunctional"ono"ers *ith the eli"ination of as"all "olecule s#ecies 2*3' Thereaction can occur bet*een an!t*o $ro*in$ #ol!"er "olecules'

P" < Pn P"


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Chain reaction #ol!"erisation#rocess b! re#eated addition of

"ono"er "olecules to $ro*in$#ol!"er chain *ithout theeli"ination of lo* "olar "ass

"olecules'

Y= Y8C508C5R

Y8C508C5R8C508C5R etc'

*here Y= is an initiator

CH2=CHRCH2=CHR=

=


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There are four t!#es of

inter"ediates for chain#ol!"erisation 2based on the t!#e ofinitiator3

Carbon free radical2initiator freeradicals3

Carbocation ion2initiator cations3

Carbanion2initiator anions3 Carbene 2initiator coordination

co"#ounds3


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Free radical process

6er! fast #rocess 2fraction of asecond3'

Re:uires initiation to start the#rocess, then #ro#a$ation to $ro*the #ol!"er chain'

Ter"ination is the last #rocess toend the #ol!"erisation #rocess'


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Molecular *ei$ht control

In #ol!"erisation #rocess, the ai" is tocontrol the "olecular *ei$ht' The follo*in$ &ariables inuence the

"olecular *ei$ht

Te"#erature the hi$her 2o#ti"u"3 thete"#erature, the shorter the ti"ere:uired to #ol!"erisation'

1ol&ent *hen a #ol!"er "olecule

#reci#itates out of a solution, it *ill not#ol!"eriBe an!"ore therefore thecorrect sol&ent is i"#ortant'


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Concentration of initiator 9oraddition #ol!"erisation, hi$herconcentration of initiator *illresult in lo*er "olecular *ei$ht

#ol!"er'Concentration of "ono"erT!#e of initiator the initiator

for"s radicals b! deco"#ositionreaction *hich has a half life*hich is de#endent onte"#erature and t!#e of

initiator'


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Cationic polymerisation

ole.n deri&ati&es C50-C5R *ith electron8richsubstituents R

"ono"ers C50- *ith double bonds containin$ heteroato"s or

hetero$rou#s

rin$s *ith heteroato"s

Three $rou#s of "ono"ers can be#ol!"erised cationicall!


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Initiators 7ronsted acids2#erchloric acid, trichloroacetic

acid, triuoro"ethanesulfonic acid,etc'3 Le*is acids 2AlCl@, TiCl?, etc'3

Coinitiators *ater, carbeniu" salts 2acet!l #erchlorate3

The $ro*in$ #ol!"er chain is #ositi&el! char$ed *hich

stabilise itself b! addition of nucleo#hilic s#ecies'

6er! fe* "ono"ers are #ol!"erised cationicall! on an

industrial scale'


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Monomer Application

Isobut!lene C50-C2C5@30 Elasto"er, adhesi&es

6in!lethers C50-C5OR Adhesi&es, te4tile aids,

#laticiBers

9or"aldeh!de C50-O En$ineerin$ #lastics

Eth!lenei"ine C!clo82N5C50C503 Pa#er additi&e, occulant

Tetrah!drofuran C!clo82O2C503?3 1oft se$"ent for

#ol!urethanes


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Anionic polymerisation

Anionic #ol!"erisation are initiated b!bases or Le*is bases such as al)ali"etals, al)o4ides, a"ines, #hos#hines,

(ri$nard co"#ounds and sodiu"na#hthalene'

The t!#e and #ro#ortion of the initiatin$s#ecies stron$l! aect the#ol!"erisation rates and the tacticit! ofthe #ol!"ers 2tacticit! refers to ho*the #endant $rou#s are arran$ed in a

#ol!"eric strand F isotactic,sindiotactic atactic


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Narro* "olar "ass distribution

E"#lo!ed for the #roduction of

ther"o#lastics es#eciall! bloc)co#ol!"ers 2s!rene8butadiene8st!rene t!#e3


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/0'@ P5Y1ICAL PROPERTIE1

The #h!sical #ro#erties of #ol!"er"aterial are lar$el! deter"ined b! Molecular *ei$ht 1tren$th of inter"olecular forces Re$ularit! of the #ol!"er structure 9le4ibilit! of the #ol!"er "olecule

The #h!sical #ro#erties include

"eltin$ #oint, $lass transitionte"#erature, solubilit!, "elt&iscosit!, tensile stren$th'


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Meltin$ #oint a te"#eratureran$e in *hich the &iscosit! of the

#ol!"er chan$es fro" a solid to ali:uid 2the #ol!"er "ust bether"o#lastic3

(lass transition te"#erature 2T$3 a

#oint *here there is a chan$e in #ol!"er "olecule chain

"otion *hich has drastic eects on stren$th'

Cr!stalline "elt te"#erature 2T"3 the cr!stalline do"ains

of a #ol!"er "elt beco"e a"or#hous'


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Tensile stren$th "easures ho*diGcult it is to brea) a substance*hen stress is a##lied to #ull ita#art' Tensile stren$th $enerall!increases *ith "olecular *ei$ht'


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The End

chapter 13 introduction to polymer

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