Recyclable superior-performing EVA-polyurea nanocomposite foams with shape memory behavior

The recycling and reuse of chemical cross-linked elastomer foam materials is a challenging issue. In this study, the “plasticizing-foaming-reinforcing” (PFR) strategy was employed to prepare recyclable ethylene-vinyl acetate copolymer-polyurea (EVA-PUA) nanocomposite foams with excellent mechanical properties and shape memory properties. EVA was mixed with polydimethyl isocyanate (PMDI), and then performing supercritical CO2 (SC-CO2) foaming process and in-situ polymerization of PMDI. The EVA-PUA nanocomposite foams prepared have excellent resilience and compression properties, like those of EVA foams with permanent chemical crosslinking. In the prepared EVA-PUA foams, PUA forms a dispersed phase of approximately 30–40 nm within the EVA phase, and there is a strong interfacial interaction between the two phases, which endows the foam material with excellent properties. Compared with pure EVA foams, the compression stress, hardness, resilience, and compression set of EVA-PUA nanocomposite foams were significantly improved. Moreover, EVA-PUA nanocomposite foams also have shape memory capabilities. The prepared EVA-PUA nanocomposite foams exhibit excellent recycling characteristics. Through melt processing, they can be recycled, and the recovered EVA-PUA nanocomposite materials have excellent re-foaming performance, and the regenerated EVA-PUA foam materials maintain excellent resilience and compression set.