SORPTION, DIFFUSION AND PERMEATION OF ESTERS INTO EPICHLOROHYDRIN ELASTOMER MEMBRANE

Sorption, diffusion and permeation of five esters into epichlorohydrin membrane have been studied in the temperature interval of 25 degrees to 60 degrees C by a sorption gravimetric method. A Fickian diffusion model was used to estimate the diffusion coefficients. The transport d ata were found to be dependent on the size of the penetrant molecules, their interactions with the chain segments of the polymer membrane, t emperature of the experiment and, to some extent, on the penetrant con centration within the membrane material. The values of diffusion coeff icients at 25 degrees C vary from 7.10 x 10(-8) cm(2) s(-1) for methyl salicylate to 7.12 x 10(-7) cm(2) s(-1) for methyl acetate. The activ ation energy for the diffusion process falls between 14.78 kJ mole(-1) to 31.05 kJ mole(-1). Heat of sorption for the aliphatic esters are n egative while for the aromatic ester, a positive heat of sorption was observed. The sorption/swelling results have been analyzed by using th e first order kinetics model. The penetration velocities have also bee n calculated. The experimental results and the calculated parameters h ave been used to study the polymer-solvent interactions. None of the s olvents used in this research has shown any degradative effects on the membrane used.