Preparation and characterization of foamed CaCO₃/eucommia ulmoides gum shape memory composites

Natural eucommia ulmoides gum (EUG) is in crystallized state due to its ordered trans-molecular structure, and it can be used as shape memory materials with low crosslink density. The foamed CaCO₃/EUG shape memory composites was prepared using Expancel 920DU40 as the foaming agent. The components and foaming properties of Expancel 920DU40 and the crystallization and melting behaviors, microstructure, shape memory properties and mechanical performance of foamed CaCO₃/EUG shape memory composites were measured by SEM, FTIR, DSC, DMA and the universal material testing machine. The results show that the shell of Expancel 920DU40 is composed of acrylonitrile and its copolymer with other monomer, and its interior is filled with liquid alkanes. The mechanical performance of foamed CaCO₃/EUG shape memory composites is related to their crosslink density and foaming extent. The melting temperature and crystalline degree of EUG and deformation rate, shape fixity ratio and shape recovery ratio of foamed CaCO₃/EUG shape memory composites all decrease with the increase of crosslink density. When sulfur content is 0.8 g, the foamed CaCO₃/EUG composite exhibites the best shape memory properties. The foamed CaCO₃/EUG shape memory composites with various shape memory abilities can be prepared via controlling their crosslink density.