Eucommia Ulmoides Gum Soft‐Hard Gradient Composite Materials with Shape Memory Property

Abstract Eucommia Ulmoides gum (EUG) is a natural polymer material with unique “rubber‐plastic duality” and good shape memory properties. In this paper, the hardness of EUG is greatly reduced by adjusting the cross‐linking density and adding physical microspheres for foaming. The results show that the more sulfur and foamed microspheres are used, the lower the hardness of EUG, the greater the deformation of the material, and the smaller the penetration force. By adjusting the amount of foaming agent, a series of lightweight and high‐toughness foamed EUG can be obtained. The EUG, natural rubber (NR) and foamed EUG are prepared into a hardness gradient composite material with a shape memory characteristic through a co‐vulcanization process, according to scanning electron microscope (SEM) observation and 180° peel test results, the three rubber materials has good binding force without the help of adhesive. Each unit of thickness of the composite material can reduce the external impact force by up to 11.6%. In addition, under heating conditions, it only takes 30 s for the crystalline EUG to return to its original shape. The prepared soft‐hard gradient sports composite material has a high reduction of external impact force per unit thickness, showing an excellent impact protection effect.