Sorption kinetics and diffusion of alkanes into tetrafluoroethylene/propylene copolymer membranes

Abstract

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...

Sorption, diffusion, and permeation of esters, aldehydes, ketones, and aromatic liquids into tetrafluoroethylene/propylene at 30, 40, and 50°c

“…Over the past several years, considerable efforts have been made in our laboratory to understand the fundamental aspects of the molecular transport of organic liquids through polymer membranes. [1][2][3][4][5] Such studies have great relevance to many applied areas of science and engineering, including those of separation processes. 6 Moreover, efforts in this direction have greatly benefited our understanding of the technological problems related to membrane-based separation processes, including pervaporation separation, 7 reverse osmosis, 8 and microfiltration.…”

Modeling of crude oil biodegradation using two phase partitioning bioreactor

“…The equilibrium sorption capacity of the TPU was defined using the immersion weight gain method as described elsewhere. 26 Briefly, polymer beads were dried in an oven (Venticell Medcenter GmbH, Germany) at 60 C for 24 h. The desired amount of dried TPU (2 g) was added to 100 mL glass media bottle containing 40 mL of the crude oil. The polymer beads were taken out of the crude oil at particular time intervals, weighed on a Sartorius balance (GD503 Class II Balance) and returned to the media bottle.…”

A review on the sustained release of cardiovascular drugs through hydroxypropyl methylcellulose and sodium carboxymethylcellulose polymers

“…In most cases, however, an intermediate situation, often called non-Fickian or anomalous diffusion, exists whenever the rates of Fickian diffusion and polymer relaxation are comparable [37][38][39][40][41].…”