Abstract: Process of lining aerosol can valve mounting cups with a gasketing composition comprising a carbon dioxide blocked polyamine dispersed in a liquid polyurethane prepolymer consisting of a free isocyanate group-containing reaction product of a polyisocyanate compound with a polyhydroxy material. The lined cups are heated for a few minutes to gel the gasket and full cure subsequently takes place without further intervention by means of ambient atmospheric moisture. The process is rapid, economical in equipment and produces gaskets which permit a significant extension of swaging specifications.