Tensile Stress Relaxation Behavior of Polyvinyl Acetate-Styrene Graft Co-Polymers and Polyvinyl Acetate-Polystyrene Mechanical Mixtures

Abstract

The tensile stress relaxation behavior of two kinds of mixed system, polyvinyl acetate (PVAc)-styrene graft co-polymers prepared by Co⁶⁰ irradiation on PVAc solutions in styrene monomer, and the mechanical mixtures of PVAc and polystyrene (PS) prepared by n-hexane precipitation from mixed solution of the polymers in benzene, were measured during a period from 30 through 6000sec. under given strains within a limit of linear viscoelasticity at various temperatures ranging from room temperature up to 170°C.
When the stress relaxation behaviors of the two systems are compared it may be suggested that for the PVAc-styrene grafted system the glass-rubber transition of the PVAc appears clearly, but that of PS slightly, while for the PVAc-PS system the transition of the PVAc appears slightly, but that of PS clearly. This remarkable reverse is attributed to the difference in the degree of mixing of the two components between the systems.
From the experimental results and previous papers^3)∼5) relating to the rheological properties of the mixed systems of two polymer components, are shown in Fig. 8 the schematic representation of temperature dependence of relaxation modulus, the shift factor, and the fractionally free volume for the two polymer components and for 50/50 mixed polymer system, and the schematic model of the mixture of the two polymer components.