Properties and mechanism of two-way shape memory polyurethane composites

Recently, smart materials have drawn wide attention from many researchers. In this paper, laminated shape memory polymer composite (SMPC) exhibiting two-way shape memory effect (SME) has been prepared by combining the pre-elongated shape memory polyurethane (SMPU) with the un-elongated elastic polyurethane (PU). Then the shape memory behaviors, laminated structure and two-way SME mechanism are investigated systematically. The results show that two-way shape memory behaviors, i.e., bending upon heating and reverse bending upon cooling, are achieved in the resulted SMPU-based-SMPCs. In addition, the SMPCs show the compositive thermal properties and dynamic mechanical properties due to their physical combination of layer-by-layer. Furthermore, the shape memory mechanism can be ascribed to the reversible change of two forces, i.e., recovery force in the SMPU layer and bending force in the elastic PU layer.