Modification of polyethylene properties by encapsulation of inorganic material

This study investigated the effect of various ceramic micro and nano fillers on the different properties (dielectric and thermal) of a polyethylene (PE) matrix. The fillers used were alumina (Al₂O₃) and boron nitride (BN). The polymer composites were prepared by ball milling and thick films containing wt. 50% of the inorganic phase were pressed. The encapsulation of the inorganic additives into the PE matrix was successfully achieved. The real part of the dielectric permittivity of a microcomposite containing Al₂O₃ was found to be close to that of the PE matrix value whereas the losses remained quite low. Thermal conductivity of PE was greatly improved: it increased by about 50% irrespective of the nature and size of the fillers. When the filler was nano BN, the breakdown strength was found to be slightly reduced by only 5%. This could be due to the size of the particles or to the high percentage of additives and the interface behavior of the fillers/matrix. Improvement of the PE surface resistance to discharges was achieved, specially with using nano-BN.