Kinetic aspects of polyester solid state polymerization.

The solid-state polymerization (SSP) of semicrystalline polyesters, a polymerization process widely used industrially to obtain polyesters with high molecular weight and/or improved quality, is critically discussed. The SSP is a process that involves chemical reactions as well as physical phenomena such as the diffusion of low MW by-products within solid particles to the particle surface and then into the gas phase, and its overall rate can be controlled by one or more of these phenomena, depending on operating conditions. The various reactions that can be involved in the SSP of polyesters are firstly discussed; then, reaction kinetics and transport phenomena are considered. Some kinetic models, proposed to describe SSP of polyesters, are then presented and critically reviewed, with particular emphasis on their capability to predict the effects of different variables. The last part of the chapter is devoted to summarize the information available for the SSP of the most important polyesters and to discuss the main features of the SSP of a given polyester.