Water permeation through elastomer laminates: 3. Neoprene/styrene-butadiene rubber

Abstract

Permeation rates and activation parameters for the transport of water and 3.5% sodium chloride solution through laminates comprised of Neoprene (CR) and styrene-butadiene rubber (SBR) have been measured at 23°C, 40°C and 60°C. Sodium chloride solution exhibited higher permeation rates than distilled water and the laminates showed a slight directional character with salt water. Also for salt water a reduction of permeation rates compared with the calculated average was observed. However, for the distilled water, essentially no directional behaviour (valving) was observed and no significant differences from calculated averages occurred, except at 60°C. These findings for distilled water are contrary to those found for other laminates. The temperature dependence of permeation rate had an Arrhenius behaviour. Observed activation energies were found to be lower for membranes which exhibited high permeation rates. Furthermore, the measured permeation rates are satisfactorily explained in the light of free volume concepts of diffusion.