Kinetic of Polymerization
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Transcript of Kinetic of Polymerization
8/10/2019 Kinetic of Polymerization
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Addition Polymerization (Chain Growth) Step Growth Polymerization (Condensation)
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Diferences between step-growthpolymerization and chain-growth
polymerizationStep-growth polymerization Chain-growth polymerization
Growth throughout matrix Growth by addition of monomeronly at one end of chain
Rapid loss of monomer early inthe reaction
Some monomer remains e en atlong reaction times
Same mechanism throughout !i"erent mechanisms operate atdi"erent stages of reaction (i#e#
$nitiation% propagation andtermination)
A erage molecular weightincreases slowly at low
con ersion and high extents ofreaction are re&uired to obtain
high chain length
'olar mass of bac bone chainincreases rapidly at early stageand remains approximately the
same throughout thepolymerization
nds remain acti e (notermination)
Chains not acti e aftertermination
*o initiator necessary $nitiator re&uired
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Steps of Radical Chain
Polymerization
$nitiation
Propagation
+ermination
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$*$+$A+$,*
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PR,PAGA+$,*
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C.A$* +RA*S/ RR AC+$,*S
+ransfer to monomerreaction
+ransfer to initiator reaction
+ransfer to sol ent reaction
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$,*$C C.A$* P,01' R$2A+$,*3sing catalyst% not initiator
.ighest reaction rate
+ermination step is 4ust disproportionation
n ironment must be pure
Reaction occurs in the cold
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nionic Polymerization50i ing Polymerization$f the starting reagents are pure and
the polimerization reactor is purged of all
oxygen and traces of water% polimerization
can proceed until all monomer is
consumed#
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C,*! *SA+$,*P,01' R$2A+$,*
3sing catalyst
'inumum two functional groups re&uired
3sually linear
'olecular weight increases slowly at low
con ersion
.igh extents of reaction are re&uired to obtain
high chain length
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6$* +$CS ,/
P,01' R$2A+$,*Reaction rate of ionic polimerization more
than radicalic polimerization
So inetics of ionic polimerization are not
calculated
7ut inetics of radicalic polimerization can beanalysed
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6inetic of RadicalicPolymerization
$nitiation-
Propagation-
+ermination-
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6inetic of RadicalicPolymerization
Ro 5 o erall rate of
polimerization
Rp 5 rate of chainpropagation
R i 5 rate of
initiation step
R t 5 rate of
termination step
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6inetic of Condensation
Polymerization&ui alent
reacti ity of
functional groups#
$t may be 8rst%
second or third
order by
depending upon#
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6inetic of Condensation
Polymerization
Assumption 5 a stoichiometry balance of monomer concentration