A “Plasticizing-Foaming-Reinforcing” approach for creating thermally insulating PVC/polyurea blend foams with shape memory function

Polymer rigid foams are highly required in the fields of wind power, transportation and construction due to lightweight and high performances. Herein, we have established a novel strategy of "plasticizing-foaming-reinforcing" (PFR) for preparing reprocessable thermoplastic/thermoset blend foams. PVC and the crosslinking monomers for polyurea (CMs) were melting mixed and foamed via supercritical CO2 (sc-CO2) foaming process followed by post-curing. The resultant PVC/polyurea blend foam presents ultra-high expansion ratio (51 times) and much smaller cell size as compared to those prepared by the traditional chemical foaming method, thus displays excellent thermal insulation performance (26.95 mW m−1 K−1) and excellent mechanical robustness, especially at lower temperature. Furthermore, the PFR strategy provides the PVC/CMs blend foam with a flexible molding ability at room temperature, allowing to form versatile three-dimensional (3D) structures. Strikingly, the microphase-separation structure of PVC-encapsulated polyurea in the cell wall endows the PVC/polyurea blend foam with excellent shape memory behavior. The PFR strategy paves a new avenue to fabricate thermoplastic/thermosetting (TP/TS) polymer blend foams in an easy-going green foaming process, which combines the performance advantages of both types of resins simultaneously possessing recyclable property.