Structural Relaxation of Quasi-Equilibrium Cross-Linked Poly(Methyl Methacrylate) in a High Temperature Glassy State
Toyomitsu WATANABE, Yukuo NANZAI and Shigeo HIRUMA
Abstract:Structural relaxation in cross-linked poly(methyl methacrylate)(C-PMMA) quite slowly cooled from the rubbery state to a quasi-equilibrium glassy state was studied at a temperature of 10C less than the glass transition temperature Tg (Tg -10C=110C). Constant-rate mechanical tension test and differential scanning calorimetry(DSC) technique were used for the observation of structural relaxation. At long times of storage at 110C for quasi-equilibrium C-PMMA, a prominent structural relaxation was found as highly progressive developments of yield stress in the tension test and endothermic peak in the DSC measurement. Imposition of a tensile strain of 0.10 to the slowly cooled specimens induced short times structural relaxation modes. Yet, in spite of the imposition of finite strain, long times relaxation modes were almost the same to that of unstrained quasi-equilibrium C-PMMA specimens. Key Words:Structural relaxation, Quasi-equilibrium glassy state, Cross-linked poly(methyl methacrylate), Differential scanning calorimetry