Question

Describe the types of polythene.

Answer 1

Polymerisation at high pressure: In this method, ethylene is polymerised at a high pressure, of the order of 1000-5000 atmospheres and at 520 K in the presence of a trace of oxygen (free radical initiator).

The polythene thus obtained possesses low density and is therefore called low-density polythene or high-pressure polythene.

Polymerisation at low pressure: thylene can be polymerised at 6-7 atmosphere pressure at 333-343K in the presence of Ziegler-Natta catalyst (a mixture of triethylaluminium and titanium tetrachloride dispersed in an inert solvent).

The polythene produced by this process features linear molecules with minimal branching. These molecules can readily self-assemble. This form of polythene has a high density and is referred to as high-density polythene.