CARBON-DIOXIDE POLY(VINYLIDENE FLUORIDE) INTERACTIONS AT HIGH-PRESSURE

The article reports on the behaviour of poly(vinylidene fluoride) in c arbon dioxide at 42 degrees C and 80 degrees C and in a pressure range of 0.1-30 MPa. Experimental techniques for the measurement of gas mas s uptake and polymer dilatation are described and the corresponding da ta are reported as mass sorption and dilatation isotherms, respectivel y. The mass uptake experiment was also used to follow the evolution of the coefficient of diffusion of carbon dioxide into the polymer as a function of pressure or concentration. An analysis for the calculation of the partial molar volume of carbon dioxide as a function of pressu re is also given, which shows that the 'apparent' partial molar volume of the carbon dioxide decreases with pressure to very low values, at high pressure. The computed values are significantly less than those f or either the liquid or the solid phases of pure carbon dioxide, and a lso lower than some data previously reported for silicone elastomers. A consideration of the origins of this apparent anomaly is given in th e conclusions. (C) 1998 John Wiley & Sons, Inc.