SYNOPSISSorption kinetics and diffusion of hexane, heptane, octane, nonane, decane, cyclohexane, and 2,2,4-trimethylpentane through tetrafluoroethylene/propylene copolymer membranes were studied using the gravimetric sorption method at 30, 45, and 60°C. Coefficients of diffusion were calculated from Fick's equation. From these data, the permeability coefficients were obtained. Analytical solutions of Fick's relations were used to estimate the liquid concentration profiles into the polymeric membranes at different times. The profiles of liquid concentrations were also simulated for the polymer-solvent systems using the numerical simulation method. Activation parameters for diffusion and sorption were evaluated and these results are discussed in terms of the molecular sizes and geometries of liquids (i.e., shape) as well as temperature. The diffusion coefficients follow a systematic decrease with increasing size of the penetrant molecules. The activation energies i.e., E D values, increase with increasing size of n-alkanes. 0 1996 John Wiley & Sons, Inc.
I NTRO DUCT 1 0 NThe molecular transport of low molecular weight liquids into polymeric sheet membranes is a subject of great practical importance in a variety of areas such as food packaging,' drug and pesticide reverse osmosis,5 and pervaporation? The main research activities in these areas have been to achieve a quantitative understanding of the factors influencing diffusion phenomena in terms of transport parameters such as sorption, diffusion, and permeation. A comprehensive understanding of the phenomena of molecular transport into polymeric sheet membranes is very essential before we envisage practical applications of these materials. An analysis of the diffusion processes in terms of concentration profiles is equally important in these areas and especially in food-packaging industries. Diffusion of small molecules into the polymer matrix is a complex theoretical problem with diverse applications. Several experimental techniques have been used to study the solvent transport characteristics of polymer mem-* To whom correspondence should be addressed. Journal of Applied Polymer Science, Vol. 59, 1857Vol. 59, -1870Vol. 59, (1996 0 1996 John Wiley & Sons, Inc.
CCC 0021-8995/96/121857-14b r a n e~.~-'~ Of these, the sorption gravimetric method, though simple, yields reliable data.l3,l4The recently developed tetrafluoroethylene (TFE)/propylene copolymer membranes (Mas-FA 100s and FA 150P TFE elastomers, manufactured by 3M) exhibit a unique combination of high-temperature, chemical, and electrical resistance properties. These elastomers are designed for use in molded goods and extruded shapes and profiles, which find applications where compression-set resistance as well as gas (e.g., N2 and COP) blistering and antiextrusion resistance are important. The TFE elastomers provide service life advantages in acids, bases, steamhot water, amines, oils, and hydraulic fluids. Other important applications of these elastomers include O-rings, seals used in hydraulic and br...
