Plastic
Plasticizers are additives which are added to a plastic material to increase its viscosity or flow properties. This is necessary to mould plastics into complex shapes which require lower viscosity at a specific temperature. Plasticizers can be in the liquid or solid form.
Plasticizers work by decreasing the length of the polymer chains. This makes the polymers more flexible. For instance, plasticizers are added to PVC to make it workable. The PVC is heated such that the distance between the molecules becomes greater due to thermal agitation. The plasticizer is then added. The molecules of the plasticizers get into the gaps between the PVC molecules. The long chains of the PVC are thus interrupted.
Plasticizers are usually esters, which are organic compounds made by the reaction of an alcohols and an acid.
Plasticizers are also added to concrete to make it more workable.