Abstract: A hydrophilic, water-swellable graft copolymer comprising polyethylene vinyl acetate (PEVA) containing between 8 and 30 wt. % vinyl acetate units, radiation graft copolymerized with an ethylenic carboxylic acid and subsequently heat treated in an aqueous hydroxide solution at a temperature greater than the softening point of the PEVA. A process for the preparation of such a polymer by radiation induced graft copolymerization of PEVA with an ethylenic carboxylic acid and subsequent heat treatment in an aqueous hydroxide solution at a temperature greater than the softening point of the PEVA is also described. The polymers of the invention are suitable for making into devices for various applications, but are particularly useful for making surgical devices, such as laparascope tubes, urethal catheters, endovascular cannuli, for endoscopic access, and as endo-prostheses. Some examples of surgical uses of such devices using the invention are described.

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.