THE PHYSICAL AGING OF AMORPHOUS AND CRYSTALLINE POLYMERS

Changing the degree of crystallinity has a pronounced effect on the me chanical behaviour and fracture toughness of a polymer due to the crys tallites acting as points of reinforcement and constraining the amorph ous regions domains between crystallites. This is apparent in that the relaxation of the glass in a partially crystalline polymer the presen ce of increasing amounts of the crystalline regions progressively redu ces the rate and extent of physical ageing which can develop and also the glass transition temperature, T-g, is raised by the presence of cr ystallinity. Enthalpic relaxation can be measured at temperatures abov e the T-g of the unconstrained amorphous regions.