(140d) Silicone Rubber Based Composites As Effective Coatings for High-Voltage Insulation Applications

Outdoor insulators are critical backbone components of the transmission line infrastructure specially in regions having inimitable weathering conditions like the Arabian Gulf countries. Heavy deposition of dust and sands or salts in coastal lines typically cause accelerated aging of the insulator coating in those regions. Therefore, there is always a demand for high-performance insulator coatings to maintain reliable high-voltage infrastructures under such harsh environmental conditions.

Room temperature vulcanized silicone rubber (SiR) has been extensively used as an efficient coating for high voltage insulators due to its high hydrophobicity, superior ability to reinstate hydrophobicity after wetting and thermal stability. However, during field operation, SiR coatings experience simultaneous high-voltage electrical stress and harsh environmental conditions, both cause swift aging and degradation of the host polydimethyl siloxane (PDMS) polymer. Addition of fillers to the PDMS is a vital aspect that help suppress the tracking and erosion of silicone rubber in severe outdoor environments like the Arabian Gulf region. To address these issues, we developed different types of nanofillers and the nanocomposites were examined for their erosion and tracking resistance performance as well as mechanical strength and thermal stability. Nanofillers include virgin and surface functionalized hydrophobic fumed silica nanoparticles, hexagonal boron nitride (hBN) and its 2-D nanosheets (e-hBN). Compatibilization of the nanofiller with host PDMS matrix (filler/matrix interface) and the thermal conductivity were the main parameters of interest which significantly affect composite's overall resistance to erosion. The Inclined Plane Tracking (IPT) test revealed that prepared composite formulations passed the industrial requirements recommended by the IEC 578 and ASTM D 2303 standards with more than 6 hours at 4.5 kV to fail. Combined aging tests (IPT, salt fog, and corona aging tests) will be also discussed which simulate the real operation conditions according to the IEC 61109 and IEEE 1024 standards. Our overall results confirmed that many of the tested composites demonstrated excellent improvement in mechanical, thermal stability, surface hydrophobicity retention, and has passed the IPT. These features would make them reliable candidates for high-voltage insulation coatings and effective mitigation of surface degradation caused by environmental contaminants deposition.