Abstract: A process and apparatus for rapidly expanding and molding carbon dioxide-impregnated polymer particles is disclosed. The process involves expanding the impregnated particles in a moving stream of pressurized saturated steam or super-heated steam, directing the resulting stream of pre-expanded particles into a mold, and molding the particles into a foamed object. Apparatus suitable for use with the process is also disclosed.

Abstract: An article having a relatively lower density polystyrene core and a relatively higher density polystyrene skin is prepared by a method in which a mold is supplied, simultaneously and/or sequentially with electrostatically charged prepuffs of a relatively higher density polystyrene and relatively uncharged low density prepuffs. The walls of the metal mold preferentially attract the electrostatically charged particles. The uncharged lower density prepuffs concentrate at the core. The thus filled mold is subjected to the heating and cooling cycle to provide a molded article having a core with a lower density than the skin.

Abstract: A method for bonding expanded polymeric parts without an adhesive. The method comprises wetting the surfaces to be bonded with water or water containing from about 1% to 2% wetting agent, positioning the surfaces to be bonded in a nonmovable abutting relationship, encapsulating the joint formed by the abutting surfaces with a mold, and, while encapsulated, passing high frequency electrical energy therethrough to effectuate a bond.