STRAIN-INDUCED LIQUID-LIKE STRUCTURES IN GLASSY-POLYMERS

Experimental evidence verifying strain-induced isothermal structural transition of glassy polymers into liquid-like structures is presented for five amorphous polymers: polymethyl methacrylate, polystyrene, polycarbonate, polyvinyl chloride and styrene-acrylonitrile co-polymer. This transition presumably accelerates the relaxation and results in the non-linear viscoelasticity in glassy polymers. The evidence was derived by an application of the Eyring equation to the steady state of plastic flow in the polymers. In this analysis, a novel method of applying the Eyring equation was used, which provided numerical values of the activation enthalpy, DELTA-H, activation entropy, DELTA-S, and activation volume, v(a), for each polymer as variables depending on strain-rate and temperature. Comparison of a unique functional relation between the rate factors DELTA-H and DELTA-S for the glass with a relation of DELTA-H vs. DELTA-S derived from the relaxation or dynamic viscoelastic data of the melt showed a good agreement for each polymer. Since the rate factors DELTA-H and DELTA-S are governed in quantity by the intermolecular interaction in the polymer system, this agreement led to a verification of the structural change of glassy polymers into liquid-like structures.