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SynopsisThe pressure-volume-temperature (PVT) properties of blends of poly(2,6-dimethyl-l,4-phenylene ether) (PPO) with polystyrene (PS) have been studied experimentally in both the glassy and melt states at 0,20,40,50,60,80, and 100% PPO content. In all compositions a strong glass transition was observed varying linearly with composition. For all but the 40% PPO composition this was the only transition, indicating molecular compatibility of the components in these blends. The 40% PPO composition showed a very weak second transition near the glass transition of pure PS. A small amount of phase separation may have occurred in this blend. The data for the glassy and melt states were fitted to an empirical equation of state based on the Tait equation. The volume of the melts at constant pressure and temperature showed a virtually linear dependence on composition. Any negative excess volume of mixing compatible with the data would have to be very small, smaller than expected from previous measurements in the glassy state. Various properties relating to the glassy and melt states and to the glass transition were evaluated and are discussed as a function of composition. It was found that most properties of the glasses could not be modeled by simple functions of composition.

SynopsisA constant volume/variable pressure gas permeability apparatus is described that provides accurate determination of permeabilities ranging from less than lo-' to lo6 centibarrers. Metal construction, variable temperature control, adjustable downstream pressure and constant volume, and a differential pressure transducer with automatic recording are design features that permit detailed permeability studies under a variety of environmental conditions. Pressure effects on polymer films have been investigated up to 1000 psi, and the relation of gas concentration to permeability has been studied by varying the downstream pressure and volume conditions. The high feed pressures have significantly shortened the time required to obtain meaningful data on low-permeability materials after steady-state conditions are achieved, and the variable-temperature control has permitted evaluation of temperature-related phenomena.