Microcellular PLA/PMMA foam fabricated by CO2 foaming with outstanding shape-memory performance

Abstract Porous shape memory polymers (SMPs) are attracting people's attention due to their extensive application prospect. Herein, a novel and flexible method to produce bio-friendly polylactic acid (PLA)/polymethyl methacrylate (PMMA) shape memory foam by a two-step CO2 microcellular foaming is proposed. The achieved foams exhibit outstanding shape memory performance, such as a maximum shape fixity ratio of 98 %, a maximum shape recovery ratio of 86 %, and further the recovery ratio remaining more than 75 % even after 10 compression-recovery cycles. The additive PMMA phases uniformly disperse with spherical morphology in nanoscale, and they result in the greatly decreased crystallinity and crystal size of PLA. Meanwhile, the extensive interfaces lead to increased crystal density. In this context, more amorphous molecular chains left in the cell wall act as reversible segments, and more numerous denser crystals act as net points, which together can decrease the resistance in the shape memory process, thus, facilitating the significant promotion of shape memory capability of the as-achieved PLA/PMMA foams. Therefore, it exhibits a promising future to produce environmentally friendly SMPs by a simple, cost-efficient, and clean microcellular foaming technology.