Performance comparison and lifespan assessment of naturally and artificially chalked silicone rubber for composite insulators

Chalking is a typical manifestation of high-temperature vulcanized silicone rubber (HTV-SR) deterioration for composite insulators. Previous studies have proposed an efficient artificial chalking method based on tetramethylammonium hydroxide (TMAH), but the quantified equivalence between artificial and natural chalking, particularly in terms of electrical properties, remains underexplored. In this paper, 5 naturally chalked (NC) samples with different lifespans and 5 artificially chalked (AC) samples with different TMAH concentrations are prepared. Then surface morphology, structure, mechanical and electrical properties of chalked samples are methodically characterized. The results indicate that the overall performance of the two kinds of chalking surfaces is similar, but AC samples treated with high TMAH concentration exhibits severe chalking. Besides, the NC process is driven by both filler precipitation and oxidative crosslink, whereas the AC process lacks internal oxidation. Further analysis based on quantum chemistry calculations reveals the silanol produced during chalking has a narrow-forbidden gap and deep traps, which degrades the electrical properties. Finally, a lifespan assessment method with 8 chalking indexes is constructed and the optimal Ridge Regression model is selected to comprehensively assess lifespans of AC samples. This study explores the chalking characteristics of NC samples, and also offers manufacturers an efficient way to evaluate the chalking resistance of new HTV-SR.