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