Enhancing the shape memory performance of self-reinforced cross-linked polyethylene composites by the optimization of the production temperature

In this study, we investigated the shape memory properties of ionizing radiation cross-linked high-density polyethylene (HDPE) self-reinforced by Dyneema fibers. We investigated self-reinforcement as a means of increasing the recovery stress (Trec), which has not been extensively researched before in the literature. Using film stacking, we produced composites with effective self-reinforcement and samples where the fibers were completely melted by high temperatures as reference samples. The composites were cross-linked by gamma irradiation with a 150 kGy dose, and we verified the cross-linked state with swelling tests. We characterized the self-reinforced composites through differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and flexural tests. We found the optimal processing temperature to be 150 degrees C, where the fibers remained intact, but adhesion was excellent. Self-reinforcement slightly decreased the recovery ratio (Rr), at the same time, it increased Trec of the samples by 111 %, as it increased the programming stress. We investigated different programming temperatures and found that higher temperatures produced higher Rr but lower Trec. We showed that through self-reinforcement we can manufacture all-polymer composites with increased Trec. All polymer composites can be fully biodegradable, biocompatible, and have lower density than conventional composites, which properties can be advantageous in future applications.