Phase continuity in polystyrene–nylon 6,10 graft copolymers

Abstract

Using a modified interfacial polymerization route, a graft copolymer of nylon 6,10 and polystyrene was prepared. First, an aqueous suspension of styrene monomer was encapsulated with nylon 6,10, followed by polymerization of the styrene to form the graft copolymer. When the material was subsequently molded below the crystalline melting point of nylon 6,10 (220°C), modulus–temperature behavior intermediate between polystyrene and nylon 6,10 was observed. However, when this graft copolymer was molded above the melting point of nylon 6,10, behavior more like pure polystyrene was observed. Phase contrast microscopy revealed that material molded below 220°C showed a continuous cellular-phase structure of about 30 microns in diameter, the interior of the cells being composed of polystyrene and the cell walls being composed of nylon 6,10. Phase inversion phenomenon was observed in the graft copolymer as the molding temperature was raised above 220°C. The nylon 6,10 phase became discontinuous, small globules being formed. This behavior is analogous to spheroidization in steel. It is thought that molten nylon 6,10 spheroidizes to attain a lower surface-energy state.