Blending of Polystyrene-Block-Poly(Ethylene-Ran-Butylene)-Block-Polystyrene with Polyethylene-Graft-Polystyrene for Cation Exchange Membrane Preparation with Enhanced Properties

A typical cation exchange membrane can be prepared from graft polymerization of styrene onto low-density polyethylene followed by sulfonation reaction. It was found that the thermoplastic elastomer polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (PS-PEB-PS) can be blended with polyethylene-graft-polystyrene (PE-g-PS) in toluene. A novel composite cation exchange membrane was prepared by sulfonating the membrane cast from the mixture solution of PE-g-PS and PS-PEB-PS. Compared with the non-blended cation exchange membrane, the blending of 10% PS-PEB-PS enhanced the ion exchange capacity, water uptake, and Mullen burst strength of the cation exchange membrane by 18.3%, 9.5%, and 26.3%, respectively. The blending also lowered the thermal expansion rate by 73.4%, making the membrane more thermally stable over temperature increase.