High shape memory properties and high strength of shape memory polyurethane nanofiber-based yarn and coil

Recently, research on shape memory-based materials has increased because of their shape programming and shape recovery attributes. Compared with shape memory alloy, shape memory polymer polyurethane (SMPU) fiber and its fabric find applications in biomaterials and wearable devices because of its easy manufacturing and flexibility. However, generating high stress to support shape recovery in the SMPU fiber is difficult, and reports about SMPU electrospun nanofiber-based yarn are rare. This study presents a novel method for preparing SMPU electrospun nanofiber-based yarn and coil using a twisting process. Our results demonstrated that, compared with the traditional melting SMPU fiber, the nanofiber interlayer friction increases the shape recovery properties of the SMPU electrospun nanofiber-based yarns and coils. Moreover, the recovery stress of aligned nanofiberbased yarn (with nanofibers' direction parallel to the tensile direction) is increased by 403%. However, aligned nanofiber-based yarns and coils can resist static and repeated tensile stress above the glass transition temperature. Based on the excellent shape recovery properties, excellent shape memory, and mechanical properties, as well as a combination of nanofibrous network structure, yarn shapes can be realized, which would be a new choice for smart fiber and textile in various applications.