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SYNOPSISCrosslinked and uncrosslinked ethylene-vinyl acetate copolymer membranes were prepared. The permeation characteristics in the pervaporation process were examined using carbon tetrachloride-acetone mixtures. Modified membranes exhibit carbon tetrachloride permselectivity, but unmodified membranes did not display the permselectivity of crosslinked polymer. Furthermore, membranes modified with dicumyl peroxide (DCP) showed a higher flux and selectivity than those of benzoyl peroxide (BP) modified ones. The effects of feed concentration, molecular size, and polarity of the permeating species on pervaporation were analyzed. The influence of crosslinking density of the membranes on pervaporation was also analyzed. The maximum separation and flux were found to be associated with an optimum amount of crosslinking agent in the membrane. A mixture of chloroform and acetone having a composition near the azeotropic region was also separated by the pervaporation technique.

SYNOPSISPolyamic acids were synthesized from benzophenonetetracarboxylic &anhydride and diamines, viz., 4,4'-diaminodiphenyl methane and 4,4'-diaminodiphenyl ether. The course of imidization of the polyamic acids both by thermal and microwave treatments was tracked by infrared spectroscopy. The mechanical properties, namely the tensile strength and toughness of the films of polyimides with varying degree of imidization obtained by the two treatments were compared. The effect of degree of imidization of polyimide coatings on adhesion to copper substrate was also studied. Nearly 100% imidization was achieved by the thermal process, whereas the maximum imidization that could be achieved by the microwave process was about 50%. In thermal imidization, the adhesion values of the coatings slowly increased, attaining a maximum value at 80% imidization, after which there was a decrease in adhesion.