EAA/RPVB blends with dual crosslinked structures and multiple shape memory properties prepared by one-step melt mixing

In this study, we synthesized ethylene-acrylic acid copolymer/recycled polyvinyl butyral (EAA/RPVB) blends using hexamethylene diisocyanate (HDI) and dicumyl peroxide (DCP) as crosslinking agents via a one-step melt blending method. This approach facilitated the formation of distinct crosslinked structures in both the RPVB and EAA phases. By adjusting the blend ratios, we engineered materials with a pseudo-interpenetrating polymer network (IPN) structure. The resulting EAA/RPVB blends exhibited a broad range of glass transition temperatures and independent crystallization/melting transitions, culminating in a remarkable triple and quadruple shape memory effects. The crosslinking reactions facilitated by HDI and DCP were systematically analyzed through torque rheological measurements, gel content assessments, and spectroscopic techniques. Our results revealed that the reactivity of HDI with the hydroxyl groups of RPVB was notably higher than that of DCP with EAA. Additionally, varying the blend compositions influenced the degree of crosslinking and network morphology, as evidenced by gel content testing, dynamic rheological analyses, and scanning electron microscopy (SEM) observations. These findings suggest that the unique structural characteristics and high crosslinking density of the blends contribute to their enhanced shape memory performance and mechanical properties.