Abstract: Typically, injection molded expandable thermoplastics exhibit imperfect surfaces in the form of mottled areas, visible flow lines, and pin holes; these imperfections are caused by the quick chilling of the surface of the expanded thermoplastic as it contacts the mold surface. This invention is a method of injection molding expanded thermoplastics free of these defects by injecting a short-shot of the expandable thermoplastic into an elastic membrane positioned within a cooled mold cavity, containing the short-shot within the membrane until a skin forms on the thermoplastic in contact with the membrane, and then permitting expansion of the thermoplastic in the cavity to form a smooth skin or surface on a substantial portion of the article.

Abstract: The discoloration occurring during commercial production of large buns or slabs of low density, flexible and semiflexible polyetherurethane foams containing chlorine-containing polymers such as polyvinyl chloride, zinc oxide and antimony oxide, in which optionally part of the chlorine-containing polymer can be replaced with a chlorinated paraffin provided a proportionate reduction is made in the amount of the zinc oxide employed, is reduced or prevented by using a small amount of a zinc salt of an organic monocarboxylic acid or an organic mono dithiocarbamic acid having from 1 to 25 carbon atoms in each acid moiety of said salt.