The viscoelastic behavior of polymethyl methacrylate

Complete stress relaxation data for polymethyl methacrylate are presented covering behavior of this linear amorphous polymer from the rubbery state to the glassy state. The effect of water on stress relaxation rates in the glassy state and in the transition region is shown. Fast cooling is shown to increase subsequent stress relaxation rates in the glassy state. The complete pattern of viscoelastic behavior may be represented by a master stress relaxation curve holding for all temperatures, but shifting along the logarithmic time scale with temperature change. The master stress relaxation curve can be represented by a distribution of relaxation times. This distribution has been derived from the master stress relaxation curve, and the master curve recalculated from the distribution has been shown to agree with the experimental master curve. The method used in calculating the distribution of relaxation times is described and can be applied generally.