ABSTRACT
The procedure by which volatiles are separated from the bulk polymer is called devolatilization and is usually performed with the polymer above its glass transition temperature, or above the melting temperature for crystalline polymers. Devolatilization of a polymer is a complex process generally involving the transport of volatiles to a polymer–vapor interface, the evaporation of the volatiles at the interface, and their subsequent removal by a vacuum system. The growth of bubbles during devolatilization depends mainly on the rate at which the volatile material can diffuse from the bulk of the polymer to the bubble surface and on the resistance of the viscous polymer melt to displacement by the growing bubble. Coughlin and Canevari presented two models to describe devolatilization during screw extrusion. The first model assumed that the process was limited by volatile diffusion within the polymer melt, and the second assumed mass transfer resistance at the polymer–vapor interface to be the limiting factor.
