HIGH-ORDER STRUCTURE AND FLAME RETARDATION EFFECT OF POLY(TETRAFLUOROETHYLENE) IN THERMOPLASTIC RESIN COMPOSITIONS

Melt-kneading of a high-viscosity resin, such as polyphenylene ether, together with poly(tetrafluoroethylene) (PTFE) at high shear rate and temperature just above the melting point of PTFE [323 degrees C (by DS C)] results in the formation of PTFE in a branched fibril form compris ing oriented trunk and branch fibers, in diameter 0.15 mu m. When a lo w-viscosity resin, such as rubber-modified polystyrene (HIPS), is melt -kneaded with PTFE at temperature lower than the PTFE melting point, P TFE in linear fibril form having a diameter of 0.05 mu m and without b ranch fibers is formed. Molded resins containing the branched-fibril P TFE undergo larger dimensional changes than those containing the linea r-fibril PTFE, when subjected to heat treatment. This indicates higher orientation of the former PTFE, and thus greater enhancement of flame retardancy in resin compositions containing HIPS, polyphenylene ether (PPE), and a phosphorus-based flame retardant.