Influence of cross-linking agent on thermomechanical properties and shape memory effect of styrene shape memory polymer

The influence of cross-linking agent content on thermomechanical properties and shape recovery behavior of thermoset styrene shape memory polymer (SMP) was investigated in this article. The SMP was polymerized by free radical reaction, with styrene and butyl acrylate as comonomers and divinylbenzene as the cross-linking agent. When the cross-linking agent content is increased from 1 to 4 wt%, the storage modulus and the glass transition temperature (T(g)) of the SMP increased correspondingly. During the glass transition, while the value of damping peak decreased as a result of the addition of the cross-linking agent, the peak width increased, and the main relaxation activation energy increased by 48.6%. When the active temperature was higher than or equal to T(g), the SMP samples containing different weight percentages of the cross-linking agent could recover their original shape. At or above T(g), SMP with varied fractions of cross-linking agent could completely recover its original shape; the recovery rate of SMP increased with the increase in the contents of the cross-linking agent. Below T(g), SMP could not recover its original shape, but the recovery angle increased as the contents of cross-linking agent increased. These results were attributed to the increase of cross-linking densities as a result of the addition of cross-linking agent.