SYNOPSISSorption and dilation properties of polymer-gas systems involving poly (ethylene-co-vinyl acetate) and N2, CHI, or C 0 2 , have been investigated at pressures up to 50 atm at temperatures of 10-40"C. Sorption isotherms for low-solubility gases (i-e., CH, and N2) can be described by Henry's law, and those for high-solubility gas (i.e., C O P ) by Flory-Huggins dissolution equation. Dilation isotherms are similar in contour to the corresponding sorption isotherms. From the obtained sorption and dilation data, partial molar volumes of the gases in the polymer were determined as a function of temperature. Thermal expansivity of dissolved C 0 2 molecules was estimated at ca. 2.4 X O C -' from the temperature dependence of partial molar volume. The expansivity is smaller than that of liquid COz and larger than those of the polymer and organic liquids. 0 1994 John Wiley & Sons, Inc. Keywords: poly (ethylene-co-vinyl acetate), gas sorption in dilation of poly( ethyleneco-vinyl acetate) due to gas sorption * partial molar volume of dissolved gases * thermal expansivity of dissolved gas * On leave from Pechiney Emballage Alimentaire, 92115 Clichy, France. CCC 0887-6266f94 fO2028l-06 estimated. The result is discussed and compared with the expansivities of liquid C 0 2 , organic liquids, and C02 molecules dissolved in other polymers.

Sorption of ethylene, ethane, and propane into poly(ethyl methacrylate) and the concomitant dilation of the polymer are measured at !SoC. Each sorption isotherm has a reverse-sigmoid shape described by the extended dual-mode sorption model, and dilation isotherms are similar in shape to the corresponding sorption isotherms. Inflection on the isotherms is due to isothermal glass transition induced by the sorbed gases, whose concentration is the glass transition concentration c •. The c. value for propane is in accord with concentration at an abrupt change found on a curve of the concentration dependence of diffusivity. Partial molar volumes of the gases at rubbery state and glassy state are evaluated from sorptive dilation data above and below c., respectively. A correlation between plasticizing ability and partial molar volume for the gases is discussed.

SYNOPSISSorption and dilation isotherms for argon in poly(ethy1 methacrylate) (PEMA) are reported for pressures up to 50 atm over the temperature range 5 4 5°C . At temperatures below the glass transition ( Tg = 61°C ) , sorption isotherms are well described by the dual-mode sorption model; and isotherms above Tg follow Henry's law. However, isotherms for dilation due to

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A previously proposed theoretical treatment to elucidate the pressure dependence of gas permeability is improved in order to apply it to polymer-gas systems in which gas dissolution follows the Flory-Huggins equation. Permeation rates of N2, CH4, and COz in poly (ethyleneco-vinyl acetate) are measured in the pressure range below 90 atm at 1O-4O0C, and the effect of pressure on permeability is found for each gas. The data are analyzed using the improved method to estimate the contributions of concentration and hydrostatic pressure to the pressure dependence of permeability. The concentration effect decreases with increasing temperature, whereas the hydrostatic-pressure effect is almost independent of temperature. Crystallinity dependence of the concentration effect is discussed in connection with high-pressure permeation data of other semicrystalline polymers reported elsewhere.

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Sorption and dilation properties of the system poly(p‐phenylene sulfide) (PPS) and carbon dioxide have been investigated at pressures up to 50 atm over the temperature range 25–85°C. The shapes of the sorption isotherms are in agreement with those predicted by the dual‐mode theory. Analysis of the sorption and dilation isotherms confirms the occurrence of an isothermal glass transition. This occurrence and its corresponding disappearance in the range investigated is discussed. Values of the partial molar volume of CO2 sorbed in PPS are calculated below and above the isothermal transition. Compared with sorption by other polymers, these values were about the same in the glassy state, but were smaller in the rubbery state. Under 50 atm CO2 at 85°C crystallization of amorphous PPS was observed. The crystallinity estimated from the solubility before and after crystallization is about 20%.