Chemistry - Addition polymerisation and polyethylene
Addition polymerisation and polyethylene
The chemical versatility of ethene (ethylene), CH2=CH2, arises from its
_highly reactive double bond,_ and is reflected in its various addition
One of the most common of these addition reactions occurs in the
production of_ polyethylene,_ via the process of _addition polymerisation,
_which involves the linking of ethylene molecules into long chains. This is
represented by the general equation
During this addition polymerisation, one of the bonds in each of the C=C
double bonds is broken, under the influence of a catalyst at high
temperature and pressure, leading to formation of covalent bonds between C
atoms on adjacent monomers (ethylene molecules).
Polyethylene has an extensive array of applications including: packaging
film for food wraps and freezer bags, coating for milk cartons, moulded
containers such as rubbish bins and a variety of containers for drink,
detergent, ice cubes, acids etc, and piping for carrying natural gas.
It can be produced in low density polyethene - LDPE - and high density
polyethene - HDPE - forms. The low density form has a greater degree of
branching on the polymer chains.
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