Plasticizers

Plasticizers

• Plasticizers are organic substances of low volatility which when added to plastic compounds improves its flexibility, extensibility and processibility.
• Thus in polymers the flexibility of polymer is achieved by internal and external plasticization.
• Internal plasticization is produced by copolymerisation which result in increase in flexibility of polymer chain or by grafting another polymer into the given polymer chain.
• Thus Poly(vinylchloride-co-vinylacetate) is internally plasticized because of increase in its flexibility.
• The large bulky groups increase the polymer motion and placement of such groups by grafting on polymer chain act as an internal plasticizers.
• In external plasticization, plasticizers are incorporated into polymers by heating or mixing or both.
• Plasticizers must be non volatile, inert, non mobile, cheap and compatible with the system to be plasticized.
• Plasticizers are classified into primary and secondary plasticizers.
• Primary plasticizer can be used as either sole plasticizer or major plasticizer.
• The secondary plasticizer are blend with primary plasticizer to produce high performance or to reduce cost.

Mode of action of plasticizers:

• The effect of plasticizer can be explained on the basis of lubricity, gel and free volume theory.
• Lubricity theory assumes that the plasticizers act as internal lubricant and cause the slip in polymer chain.
• Gel theory is applicable to amorphous polymer and it assumes that the polymers such as PVC has many intermolecular attraction which is weakened by presence of plasticizers such as DOP.
• Free volume theory assumes that addition of plasticizers increase the free volume of polymer.Additives