Influences of high-impact polystyrene loading on the foaming behavior andflame-retardantproperties of polyphenylene oxide composites blown withCO(2)

摘要

Polymeric foam with high expansion ratio, well-defined cell structure, and excellent flame retardant properties is essential for broadening its applications. Polyphenylene oxide (PPO) is a kind of cost-effective engineering plastic with excellent flame retardancy, anti-dripping behavior, and good mechanical strength, but suffers from its poor processability. In this study, microcellular PPO composite foams were fabricated by applying a solid-state foaming technology using compressed CO(2)as the blowing agent. High-impact polystyrene (HIPS) phase was introduced with the aim to improve the fluidity and foaming ability of PPO composites. It was interesting to find that the 18-48% HIPS loading significantly increased the expansion ratio, that is, 1.8-3.3 versus, 10.8-14.3, and broadened the optimum foaming temperature of PPO composite foams, attributing to the miscible character between PPO and HIPS and excellent foaming ability of HIPS. Furthermore, the as-prepared PPO/HIPS composite foams exhibited high limited oxygen index (LOI) of 22.0-29.9%, low horizontal flammability rate (HFR) of 60.5-141.2 mm/min, and anti-dripping behavior, and the void fraction was verified to be a critical parameter to determine the flame retardant performance of the composite foam. Besides its lightweight and excellent flame retardant properties, PPO composite foams also presented uncompromised tensile properties and well-defined thermal insulation properties.