Time and Temperature Dependence of Amorphous Polymer Dynamic Properties after a Small Static Deformation

Abstract
The physical aging concept is generally used to explain the typical behavior of amorphous glassy materials such as amorphous polymers after different annealing or temperature quenching . In this work it is evidenced by measuring, on already aged specimens, the effect of deformation on the dynamic mechanical properties of several amorphous polymers (polycarbonate, polyetherimide and a styrene butadiene copolymer). For a static extension of 3 %, E' at an amplitude of ≈ 0.01 % was determined from 0.4 to 25 Hz, and for aging times, t_e, in the 10 to 7000 s range or longer. Such data determined at different temperatures were used to evaluate the aging rate d log E'/d log t_e, which was found to be independent of frequency and t_e over the ranges covered. Aging rate was found to increase with increasing temperature towards the nominal T_g of the polymer. Several peaks were observed and attempts were made to attribute them to different moieties of the polymer chains by comparison of the secondary relaxations. Furthermore, the effects exerted by small solid particles or short fibers in composite materials based on the same polymer matrix were discussed.