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Polymers_29
Chapter
G) CLASSIFICATION OF POLYMERS Uses: It is used in making sheets, brisUes for brushes and in
0 Classification based on source textile industry
a Natural polymers : These polymers are found · I ts . 0 Nylon 6:
· . . in Pan and animals. Examples are proteins starch rubber etc.
b Semi-synthetic polymers : Cellulose-derivative ' '
· . ers . Th s as ce11u1ose acetate and cellulose nitrate are semi-synthetic polymers. 0
c. Synthetic polym · ese are man made polymers examples are Buna-S, nylon 6,6, polythene etc. II H
533-543 K ➔ -tC-fCH t,N+,
H,O z• •
@ TYPE OF POLYMERISATION REACTION Nylon 6
Caprolactam
A. Addition polymerlsatlon or chain growth
• High density polythene: Use: It is used in manufacture of tyre cords, fabrics and ropes.
polymerisation
TlCl.,(C,H,),AI ➔ ll'H CH .l.
• The molecules of the same monomer or different nCH2 = CH2 (333-343) K (6-7) aim "'\"-' 2 - 2Tn ii. Polyesters: These are condensation products of
monomers add together on a large scale to form a High density polythene
dicarboxylic acids and diols.
polymer. • Catalyst liCI., (C2H5),AI is called Ziegler-Natta catalyst
• The polymer obtained has high density due to close
• Monomers used are unsaturated compounds, e.g.
alkenes, alkadienes and their dirivatives
• Chain growth can take place through the formation of
packing.
• These are also called linear polymers.
,HOCH, - CH,OH •~;j-OCH, - CH, - 0 -8--@--t
(Ethylene glycol) COOH Terytene (dacron) ·
either free radicals or ionic species. • It is also chemically inert, more tough and hard.
(Terephthallc acid)
• The addition polymers formed by the polymerisation ii. Polytetrafluoroethene (Teflon)
of a single monomeric species are known as Use: It is _used in blending with cotton and wool fibres.
nCF =CF Catalyst ➔ fCF - CF t,
homopolymers. 2 ~ high pressure ?eflon 2n iii. Phenol formaldehyde polymer (Bakelite)
·"T"
Example : Polythene Uses: It is used in making oil seals, gaskets and non-stick OH OH OH OH
• The polymers made by addition polymerisation from
two different monomers are termed as copolymers.
Example: Buna-S
surface coated utensils.
iii. Polyacrylonitrlle:
CN
@ + CH,O ;;.·, @("o" ·~OH
nCH = CHCN Polymeiization ➔ [-CH2 - 6H-J
OH OH
n CH2 = CH - CH = CH2 + n C,H5CH = CH2 2 Peroxide catalyst n
1.3-&Jladiene Styrene H OH OH OH
Uses: It is used as a substitute for wool in making
♦ commercial fibers as orion or acrilan. n OH
-Hc~cH-
-4 ' l_8J l_8J l8J •
C,H,
I B. Condensation polymerisation or step growth Novolac
-(CH2 - CH = CH - CH2 - CH - CH,t. · polymerisation
Butadiene-styra copolymer (Buna-S) • It generally involves a repetitive condensation reaction • Novolac on heating with formaldehyde undergoes cross
• Preparation and uses of important addition polymers between two bl-functional or tri-functional monomeric linking to form bakelite
i. Polythene: There are two types of polythene units. • Bakelite is thermosetting polymer which can not be reused or
Low density polythene: • This is also called step growth polymerisation. remoulded OH
• It is obtained by the polymerisation of ethane under Preparation and uses of some polymers obtained by
high pressure of 1000 to 2000 atmospheres at a condensation polymerisation.
temperature of 350 K to 570 K in presence of a · I. Polyamldes: These polymers possess amide
peroxide initiator. · linkages and are called nylons.
• It is obtained through free radical addition and H- • Nylon6,6:
n COOH(CH2)4COOH + n NH 2(CH 2)6NH2
atom abstraction.
553 Kl High Pressure_ 0 O OH OH OH
• It has highly branched structure. . T II II Uses: It is used for making combs, electrical switches and
• They ar:e chemically inert, tough but fleXJble and fNH - (CH,-teNH - . C(CH 2); Ct. + nH2O handles of various utensils.
poor conductor of electricity ·
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