Abstract
As sequel of the previous paper relating the rheological properties of the mechanical mixture of two polymer components to the degree of mixing, the temperature dependence of tensile stress relaxation of the two types of mixed systems, polyvinyl acetate-polymethyle methacrylate system and polyvinyl acetate-lightly crosslinked polymethyle methacrylate system, was investigated over a temperature range covering enough the glass-transition temperatures of the two polymer components.
The procedure, the so-called “time-temperature superposition” was carried out in comparison with several parameters, such as fractional free volume and its thermal expansion coefficient which were temporarily determined on a basis of the free volume concept on the viscosity in relation to the William-Landel-Ferry's equation, with those of the individual polymer components.
Although the fractional free volume and its thermal expansion coefficient thus determined for the mixed systems were just of apparent, the results may, at least qualitatively, deny the simple additivity of the free volumes of the two polymer phases and suggest the existence of a sort of physical interaction between the phases, i. e., the internal pressure induced by one phase to the other due to the difference of thermal expansion coefficient between the phases.
