The Secretary of State for Defence in Her Brittanic Majesty's Government

Jonathan W Ramsay

Peter J Fydelor

Ronald A Miller

Barbara J Ringrose

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.

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London, United Kingdom

Jonathan W Ramsay