Degradation and aging of polymer blends I. Thermomechanical and thermal degradation

The commercial importance of polymer blends implies interest in knowledge of their degradation behaviour under environmental stresses. Processes accompanying thermomechanical and thermal degradation of blends of commodity polymers are reviewed. Thermomechanical degradation, characteristic of melt processing, includes reactions between component macromolecules and relevant macroradicals. Cross-reactions giving grafted copolymers occur in some blends. Thermal degradation in an inert environment includes cross-reactions between macromolecules and low-molecular weight molecules or free radicals migrating over phase boundaries. As a consequence, thermal stability of the component polymers is either reduced or increased, according to the reactivity of involved species.