Dynamic mechanical method in the characterisation of solid polymers

The basic theory behind dynamic mechanical measurements is explained and dynamic moduli defined. The effect of changing the major variables temperature and frequency in a region of polymer relaxation is discussed. Commercially available instrumentation is briefly reviewed with the merits of the various systems explained. Measurements on random and block copolymers are compared and the power of the technique for distinguishing phase separation and partial compatibility is emphasised. Crystalline polymers present interesting two-phase composites, with the crystalline phase and related structures contributing specific relexations particularly in the region below the melting point. Carbon-reinforced epoxies represent more traditional composites where the engineering data obtained directly from the measurements are as important as the relaxational characteristics. The power of frequency multiplexing in fully characterising molecular relaxation is illustrated with these materials and activation energies derived from a single thermal scan.