Shape memory function of trans-1,4-polyisoprene prepared by radiation crosslinking with a supercritical CO2 foaming

Abstract

As a class of smart material, shape memory materials have a great attention due to its potential applications in sensors, textiles, aerospace engineering and medical devices. Herein, we prepared a trans-1,4-polyisoprene (TPI) foam with shape memory properties by radiation crosslinking with the supercritical CO2 foaming method. Firstly, TPI micro-crosslinks were prepared by radiation crosslinking, and then supercritical foaming were carried out. The effect of doses (30 kGy–150 kGy) on TPI foams was investigated. The shape memory behavior of the TPI composite material depends on the crystallinity of the material. The radiation crosslinking method is more suitable to improve the shape memory properties of TPI foam materials. The increase in the dose increases the degree of crosslinking of the material, however it will not crystallize the material significantly. The pores of the microcellular foam material always have a closed-cell structure with the increased dose. While the shape of the cell changes from a honeycomb structure to a circular structure, the cell density increases continuously along with the decreased cell size, and the cell wall changes significantly. As the cell wall thickness increases, the density also increases; the recovery rate of the material increases. The material can achieve a recovery rate of 85% or even ~100% in only 6 s at 100 kGy dose. TPI foamed materials with a high dose can undergo shape recovery at relatively low temperatures. Dielectric study reveals that the introduction of cells can greatly reduce the dielectric constant and dielectric loss of the materials, which improve the insulation performance of TPI. The prepared TPI shape memory materials can be applied in the field of item packaging with good protection and recyclability.