The influence of chemical structure on the relaxation properties of heat-resistant aromatic polymers

Data concerning the experimental method for the estimation of the mechanical workability of heat-resistant polymers, based on relaxation measurements, as well as concerning procedures for the fitting of stress relaxation and creep curves with the aid of new memory functions are surveyed. The influence of the chemical structures of various heat-resistant polymers (aromatic polyethers and polyamides, polyimides, polybenzoxazoles, polyoxadiazoles, etc.) on their relaxation behaviour is analysed in detail. Attention is concentrated on the relaxation transitions manifested in the glassy state. The mechanism of the deformation and relaxation in heat-resistant polymers, investigated with the aid of the positron annihilation method, is described. The relaxation behaviour of heat-resistant aromatic polymers down to the temperature of liquid helium is considered. Attention is drawn to the relaxation behaviour. The bibliography includes167 references.