Polymerisation of ethylene is carried out at high temperature and at high pressure in presence of small amount of acetyl peroxide as initiator.
(1) Formation of free radicals : The first step involves clevage of acetyl peroxide to form two carboxy radicals. These carboxy radicals immediately undergo decarboxylation to give methyl initiator free radicals.
(2) Chain initiating step : The methyl radical thus formed adds to ethylene to form a new larger free radical.
(3) Chain propagation step : The larger free radical formed in the chain initiating step reacts with another molecule of ethene to form another big size free radicals and chain grows. This is called chain propagation step.
The chain reaction continues till thousands of ethylene molecules are added.
(4) Chain terminating step : The continuous chain reaction can be terminated by the combination of free radicals to form polyethene.
