High Temperature Effects on the Nanoindentation Behaviour of Polyethylene-based Nanocomposites

This paper illustrates the dependence of the near-surface properties of polyethylene-based nanocomposites on the temperature and the nanofiller content using nanoindentation techniques. The specimens were manufactured by melt processing a premixed blend of 75 wt.% ultra-high molecular weight polyethylene (UHMWPE) and 25 wt.% high-density polyethylene (HDPE) with 0.5, 1 and 3 wt.% multiwalled carbon nanotube (MWCNT) or 0.5, 1 and 2 wt.% inorganic clay. The results showed that the incorporation of MWCNT can increase the indentation resistance, with indentation resistance increasing with filler content. The indentation resistance was significantly increased with the addition of 1 wt.% clay nanoparticles. However, increasing the volume fraction of clay nanoparticle further resulted in a reduction in the indentation resistance. The indentation hardness and elastic modulus were significantly increased with the incorporation of both MWCNT and clay nanoparticles at room temperature. At elevated temperatures, up to 65°C, a significant reduction was observed in the indentation resistance, hardness and elastic modulus, which indicated a thermal softening of the materials. However, it is interesting to find that the presence of the nanoparticle can enhance these properties at both room and high temperatures. Therefore, it is important to consider these variations in the near-surface properties of polyethylene-based nanocomposites when using such materials at various ambient temperatures.