Abstract: An Electrolytic cell having a separator positioned between a positive electrode and a negative electrode is disclosed in which the separator is a moulding of polymer material derived from a particulate polymer material having a polar graft-copolymerized surface. The separator may be deposited as a coherent film of the surface of an electrode by sintering the particulate material into a coating around the electrode using heat and/or pressure. Alternatively a shaped article such as a case, envelope, sheet film or the like may be prepared and used to wrap around or encase an electrode.

Abstract: A method of treating a hydrophilic polymer film is described in which the film is immersed at a temperature greater than 80.degree. C., and preferably greater than the crystalline melting point of the polymer, in a liquid capable of swelling the polymer. Polymers to which this method can be applied include graft copolymers of for example polyethylene, polypropylene, polytetrafluoroethylene, and nylon with acrylic or methacrylic acid. The films when treated have decreased electrical resistance and increased hydroxyl ion permeability and are then useful as battery separators and in other semi permeable membrane applications.