Reversible Plasticity Shape Memory Effect in SEBS/Crystallizable Paraffin: Influence of Paraffin Content

Polymers with reversible plasticity shape memory effect (RPSME) have attracted considerable attention due to their simple programming and large deformation. However, the exact mechanisms of RPSME are still not thoroughly understood. In this work, the RPSME of SEBS/crystallizable paraffin was investigated by comparatively analyzing the performances and microstructures of samples with different paraffin content. It was found the shape fixing ratios (R(f)s) of samples increased with the paraffin content, and interestingly, a significant improvement in R-f was observed when the paraffin content exceeded 60 wt%. Tensile test results showed that the deformation characteristics of samples changed from elastic to plastic as the paraffin content increased above 60 wt%. By exploring the crystallization behaviors of paraffin in various SEBS/paraffin samples, it was revealed that the microstructures of SEBS/paraffin were different when the paraffin content was below 50 wt% and above 60 wt%. In samples with low paraffin content (below 50 wt%), nearly all paraffin was co-crystallized with ethylene-co-butylene (EB) chains and its crystallization was severely restricted; while in samples with high paraffin content (above 60 wt%), excess paraffin appeared and this part of paraffin crystallized on the template of the EB/paraffin co-crystals, which might be responsible for the elastic-to-plastic transition and the sharp increase in R-f. Based on the above results, a possible structural model was proposed to explain the exact mechanism of RPSME in SEBS/paraffin.

Automated summary

This study investigated the reversible plasticity shape memory effect (RPSME) of SEBS/crystallizable paraffin. The results showed that samples with higher paraffin content exhibited better shape fixing ratios (R(f)s) and displayed a transition from elastic to plastic deformation. The microstructures of SEBS/paraffin also varied with different paraffin content. A structural model was proposed to explain the mechanism of RPSME in SEBS/paraffin.