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Thermoplastic elastomer, which has important characteristics for cable insulation, was developed by melt blending of polypropylene (PP) with ethylene propylene diene monomer (EPDM) at various blend ratios together with SiO 2 , TiO 2 and ZnO nanofillers at fixed loading of 2 vol.-%. The influence of EPDM content and the presence of nanofillers in the blend on burning rate, hydrophobicity and dielectric breakdown strength were investigated. Burning rate of PP/EPDM/ZnO was significantly reduced, implying that there was an improvement in fire retardancy with the addition of ZnO nanofillers in the polymer blend. Both SiO 2 and ZnO filled system showed an improvement in hydrophobicity. Furthermore, dielectric breakdown strength showed higher value in EPDM rich blends. In addition, the presence of nanofillers deteriorated the dielectric breakdown strength of PP/EPDM nanocomposites.

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The electrical and thermal properties of two series of composites, single-filler aluminum (Al) and silver (Ag) and hybrid-filler Al/Ag-filled high-density polyethylene (HDPE) composites, are reported. The composites were prepared by mixing using an internal mixer followed by compression molding. Studies on the electrical properties of single-filler composites showed an insulator-to-conductor transition in HDPE/Ag and HDPE/Al between 45-55 wt% and 55-65 wt% filler loadings, respectively. This is due to the formation of conductive paths that spanned throughout the polymer matrix, as revealed by morphology study. Thermogravimetric analysis results indicated that the degradation temperature of the composites decreased with the incorporation of 15 wt% Al-and Ag-fillers but increased slightly after the addition of 55 wt% of the filler. Investigation on the effect of hybrid composites showed that high-electrical conductivity was achieved, exhibiting percolation phenomenon in HDPE/80Ag20Al and HDPE/70Ag30Al composites where in these composites, 20% and 30% from 55 wt% of Ag were replaced with Al fillers, respectively. Furthermore, thermal stability significantly increased when hybridization was conducted to form the composite.

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