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

Abstract

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 (σrec), 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 ◦C, where the fibers remained intact, but adhesion was excellent. Self-reinforcement slightly decreased the recovery ratio (Rr), at the same time, it increased σrec 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 σrec. We showed that through self-reinforcement we can manufacture all-polymer composites with increased σrec. All polymer composites can be fully biodegradable, biocompatible, and have lower density than conventional composites, which properties can be advantageous in future applications