THE PHYSICAL AGING OF AMORPHOUS AND CRYSTALLINE POLYMERS

Changing the degree of crystallinity has a pronounced effect on the mechanical behaviour and fracture toughness of a polymer due to the crystallites acting as points of reinforcement and constraining the amorphous regions domains between crystallites. This is apparent in that the relaxation of the glass in a partially crystalline polymer the presence of increasing amounts of the crystalline regions progressively reduces the rate and extent of physical ageing which can develop and also the glass transition temperature, T-g, is raised by the presence of crystallinity. Enthalpic relaxation can be measured at temperatures above the T-g of the unconstrained amorphous regions.