Dual- and triple-shape memory properties of cross-linked recycled polyvinyl butyral/polyvinyl chloride binary blends

Various ratios of recycled polyvinyl butyral (RPVB)/polyvinyl chloride (PVC) blends were prepared using a simple melt blending technique through incorporating RPVB, PVC, and hexamethylene diisocyanate (HDI) capable of cross-linking with RPVB, to achieve a broad glass transition region. The thermal transitions, microstructure, and their correlation with the shape memory properties of the blend were systematically studied. The results indicate that the blends with a microphase-separated structure exhibit high miscibility, as well as a wide range of glass transition that expands with increasing PVC content. When the PVC content is low, the entire transition region shows a primary transition, while at higher PVC contents, the broad transition region consists of two closely spaced but distinguishable transitions. The blends demonstrate good dual and triple-shape memory performance. The RPVB cross-linked network and the degree of vitrification for the PVC and RPVB phases are crucial factors in controlling temporary shape recovery and fixation. The RPVB/PVC blend with 20% (by weight) PVC content featuring an island-like structure exhibits the best triple-shape memory performance and mechanical properties.