The effect of temperature on physical aging of classy polymers

Constitutive equations are derived for the linear viscoelastic response of amorphous glassy polymers subjected to physical aging. Stress-strain relations are applied to fit experimental data for poly(methyl methacrylate), poly(styrene-co-acronitrile), and poly(vinyl acetate) in tensile relaxation tests and in torsional dynamic tests at various temperatures. Fair agreement is demonstrated between observations and results of numerical simulation. It is revealed that an increase in the annealing temperature results in an increase in the rate of relaxation and a decrease in the apparent rate of structural recovery. (C) 2001 John Wiley & Sons, Inc.