Construction of interfacial reinforcement structure of polyphenylene sulfide foam for bead foaming molding

Polyphenylene sulfide (PPS) is a most widely used special engineering plastic, while the foam research is of great significance to expand its application and meet the requirements in aerospace, automobile, etc. In this work, the skinless PPS foam bead (S-PPS) was first prepared by surface-constrained sc-CO₂ foaming method. Compared with the regular PPS foam bead, the solid skin layer of S-PPS foam bead is completely eliminated, exhibiting obvious honeycomb porous structure, while the cell density of the surface was even higher than that of the core layer. Furthermore, PPS-based foam was prepared with the surface adhesion-assisted molding method of foam beads by using epoxy resin (EP) as the interfacial adhesive layer. The surface affinity and adhesion strength of foam bead with EP reasin was enhanced by formation of surface porous structure, while compared with regular PPS@EP foam with clear adhesion interface between the foam beads and EP phase, for S-PPS@EP foam, the EP phase penetrated and anchored into the micropores on the surface of S-PPS beads, forming a strong mechanically interlocked structure, significantly enhancing both interfacial physical and chemical interactions between the two phases and thereby improving the overall mechanical performance of the bonded foam samples. With increasing adhesive content and interfacial layer thickness, the difference in compressive property between the two types of samples progressively widened. Specifically, the compressive strength of the S-PPS@EP foam samples was improved by approximately 42 % compared to the PPS@EP foam samples. This work provides a novel strategy for preparing special engineering plastic foam.