Chapter 17 - Polymeric Plasticizers

Abstract

This chapter focusses on polymeric plasticizers. A plasticizer is a chemical used to reduce the stiffness of an amorphous (glassy) thermoplastic resin and improve the processibility of the product. The result of incorporating a plasticizer is a product that has a lower degree of stiffness than the parent thermoplastic. This chapter includes some information on low molecular weight “polymeric” plasticizers, which are usually liquids as well as the true polymeric plasticizers, which are high molecular weight solids. Low molecular weight plasticizers are used to enhance the flexibility of a rigid resin or to improve its processibility. If the rigid resin has a low T g (glass transition temperature), both effects are obtained, and if the rigid resin has a high T g and a high melt viscosity, the plasticizer may produce a dramatic improvement in the processibility of the melt with a relatively minor decrease in the rigidity of the resin. The fundamental molecular effect of a monomeric plasticizer is to interact on a molecular scale with the segments of the polymer to speed up the viscoelastic response of the polymer. A polymeric plasticizer produces exactly the same result and increases the molecular mobility of the polymer chains. This increase in mobility produces a lowering of the T g .