LDPE/EPDM Blends as Electrical Insulators with Unique Surface, Electrical and Mechanical Properties

The mechanical, thermal, morphological, dynamical mechanical and electrical properties of polymeric insulators are tested and reported. Low density polyethylene (LDPE), ethylene-propylene-diene monomer (EPDM) and blends of LDPE/EPDM are known polymers for use as low, medium and high voltage insulators. Several formulations containing EPDM and LDPE were prepared. EPDM was blended with LDPE in different weight ratios of LDPE/EPDM (100/0, 80/20, 60/40, 50/50, 40/60, 20/80, 0/100). The change in Haake-viscosity mixing torque with time for different blend compositions was obtained. The torque at any time is dependent on the blend composition. For EPDM the observed torque is directly influenced by its cross-linking density. However, for LDPE or blends of high percentage of LDPE the influence of cross-linking density on torque is relatively low. The mechanical properties of cross-linked EPDM are weaker than LDPE. Therefore changing the cross-link density of EPDM will not affect the blend properties significantly especially at high LDPE content. A drop shape analysis system G 10 (Kruss-USA) was used for hydrophobicity studies. Studies illustrate that in LDPE/EPDM blends, tensile strength of the blends are higher than either polymer component alone. But the synergism effect in LDPE/EPDM compound is stronger than HDPE/EPDM. Also the blends of LDPE/EPDM show good breakdown voltage strength and heat resistance comparing to LDPE. The result of mechanical measurement shows that mechanical properties such as tensile strength, modulus and elongation-at-break of blends can be enhanced with increase in LDPE in the formulation. Also tests were conducted to study various properties (mechanical, surface, electrical) under accelerated ageing condition. Because the life time of these compounds are generally too long to wait for a verdict on their behaviour in use. The ageing results show that mechanical properties follow the same trend as pre-ageing stage.