Building Materials, Third Edition

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The addition polymerisation reactions can take
place only by the application of heat, light, pressure,
or catalyst.
The thermal initiators are most commonly used
to generate radicals to imitate polymerisation.
Peroxide compounds (containing 0–0 bonds) like
acetyl peroxide (Ac 2 O 2 ), benzoyl peroxide (Bz 2 O 2 )
and azO compounds etc. used as initiators. The
initiated polymerisation process does not last
indefinitely because the molecules must be available
in the immediate vicinity at ends of the chains.

Co-polymerisation is a type of addition poly-
merisation where simultaneous polymerisation of
two or more chemically different monomers takes
place resulting in the formation of a polymer
containing both monomers linked in one chain. An
example is shown in Fig. 16.5.

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(i) Ethylene



Monomer



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C CCCCCCC

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(ii) Polymerizaion

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(i) Vinyl chloride (i) Styrene

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H H H H H H H H HHHHHHHH

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C C C C C C C C CCCCCCCC

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H ClHClHClHCl H HH H

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– C– C –C– C –C– C –C– C– – C–C C–C–C–C C–C–

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H Cl H Cl H Cl H Cl H H H H



Monomer


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Monomer

(ii) Polymerization (ii) Polymerization