PS/PPO foam with excellent comprehensive properties prepared by integrated foaming and sintering strategy with microwave-assisted

Expanded polystyrene (EPS) foam, as the earliest and most common foam part, holds the largest market share in the bead foam industry. However, its poor mechanical and thermal performance significantly hinders its widespread application. Introducing high-performance polymer polyphenylene oxide (PPO), which is well-compatible, can markedly enhance the properties of polystyrene (PS). Nevertheless, the elevated processing temperature poses a challenge for sintering the beads of PS/PPO. In this study, we propose a microwave-assisted polymer integrated foaming and sintering strategy (IFS strategy). Benefiting from the selective heating properties of microwaves, PS/PPO bead foams after rapid depressurization foaming can be sintered into robust foam parts in an extremely short time, with the simultaneous expulsion of microwave absorbers. The compressive performance of PPO-enhanced PS foam is improved by 155% compared to PS foam and 707% compared to expanded polystyrene (EPS). Additionally, the foam also has excellent temperature resistance (over 140°C), flame retardancy, and thermal insulation (thermal conductivity of about 40 mW/m·K). This approach provides a feasible pathway for the green, efficient, safe, energy-saving, and sustainable preparation of high-temperature processing and high-performance polymer bead foam parts.