Effects of stearic acid and thermal treatment on morphology and dielectric properties of UHMWPE/POSS composites prepared by ball milling

For the last decade, there has been lots of interest in the development of nanodielectrics as these materials may present superior dielectric properties when compared to traditional composites. However, the success of these materials relies on a proper dispersion of nanofillers within the matrix. In this work, UHMWPE/POSS composite of Ultra-High-Molecular Weight PolyEthylene (UHMWPE) with 5% wt Octaisobutyl Polyhedral Oligomeric SilSesquioxanes (POSS) was prepared by ball milling. In order to enhance the dispersion of POSS within UHMWPE, two routes were tested: 1) stearic acid in a concentration of 1% wt (versus POSS filler) was added to UHMWPE and POSS blend during ball milling; 2) a thermal treatment on UHMWPE/POSS composite at a pressure of 6.3×10⁶ Pa and an average temperature of 453 K for 7200 s was carried out. The resulting composites were tested using optical microscopy, heat-flux differential scanning calorimetry, broadband dielectric spectroscopy and short-time breakdown. The results showed the first route seemed to have little effect on enhancing the dispersion of POSS within UHMWPE matrix nor the dielectric properties of UHMWPE/POSS composite. The results also showed the second route seemed to have a positive effect on enhancing the dispersion of POSS within UHMWPE matrix yet a negative effect on the dielectric properties of UHMWPE/POSS composite.