Plasticisers are substances that increase the flexibility of the polymer by weakening the intermolecular forces between polymer chains.
Different products require different degrees of flexibility – for example food wrap needs to be flexible while window frames need to be rigid. Both can be manufactured using polychloroethene, but plasticisers have been added to the polymer in food wrap (Clingfilm).
The polymer chains are held together by Intermolecular forces – this is a rigid polymer.
Figure 5.2 Rigid polymer
The plasticiser modules keep the chains apart, so they have weaker intermolecular forces. This can be seen in Figure 5.3.