Shape memory characteristics of injection molded, cross-linked all-polyethylene composites

In this study, we investigated the shape memory properties of a novel self-reinforced polymer composite (SRPC). Chopped Dyneema® SK76 fibers were mixed with high-density polyethylene (HDPE) resin, and samples were produced by injection molding. To allow the fibers to keep their shape and reinforce effectively, we cross-linked them with gamma irradiation (100, 200, and 300 kGy absorbed doses). In the second step of irradiation, we irradiated the composites with doses of 50, 100, 150, and 200 kGy to give them shape memory properties. Soxhlet extractions, differential scanning calorimetry, and scanning electron microscopy revealed that the fibers cross-linked and kept their structural integrity through processing. We confirmed the reinforcing effect of the fibers with flexural tests and by dynamic mechanical analysis. In free recovery experiments, samples had recovery and fixity ratios above 79%. With the highest dose, recovery stress increased by 26%. We showed the viability of this novel method of self-reinforcement in the production of shape memory polymers (SMPs) with improved characteristics.