Variation of Dynamic Viscoelasticity in Glassy Polymethyl Methacrylate Being Uniaxially Stretched by Creep Stress and Constant Rate Tension
Shin'ya YOSHIOKA, Hiroyuki TACHIBANA and Yukuo NANZAI
Abstract: The complex shear modulus, G*=G'+iG", of glassy poly(methyl methacrylate) (PMMA) has been measured during creep elongation and constant speed elongation where plastic flow is observed. In creep experiments, the stress level is chosen so that it agrees with that of the steady plastic flow observed by constant speed experiments. In the state of steady plastic flow, value of G* obtained by the creep elongation and the constant speed elongation agrees with each other. This agreement leads to the conclusion that molecular structures developed in steadily flowing glass do not depend on the deformation history. At the lowest strain rate or the lowest creep stress, G' gradually increases with elongation and exceeded the value for undeformed sample. This result shows that the polymer glass can be hardened during post-yield plastic flow. Key Words:Glassy polymer, Large deformation, Dynamic viscoelasticity, Creep, Constant rate tension, Structural change