Super-strong polyphenylene oxide/polyphenylene sulfide blend foam fabricated by constructing highly oriented crystalline structure

Developing high-performance polymer foams is essential for aerospace applications in harsh conditions. Super-strong polyphenylene oxide/polyphenylene sulfide (PPO/PPS) blend foams were fabricated via establishing a combined solid-phase drawing/sc-CO2 batch foaming method to construct an oriented crystalline structure. The incorporation of poly(styrene-co-glycidyl methacrylate) (SG) improved interfacial compatibility between PPO/ PPS phase, and the stretchability of the blend was enhanced. Under appropriate draw ratio (DR) and PPS content, a relatively high dissolved CO2 amount resulted in increased cell size, cell density and expansion ratio, while the cell structure was oriented along drawing direction, and fibrillar structures formed and entangled on cell walls. Increasing DR and forming more PPS crystals facilitated the retention of orientation structure, and for oriented foam with 200% DR, the strength and modulus increased by 86% and 140%, respectively compared with isotropic foam. The dense cell structure and oriented fibrillar structure contributed to significantly improved mechanical strength for PPO/SG/PPS foams.