Erosion by acid rain, accelerating the tracking of polystyrene insulating material

Abstract

Because outdoor insulating materials in service are subjected to numerous wet and dry cycles, it is necessary to establish their performance in acid rain. The erosion effect of acid rain on atactic polystyrene insulating material is investigated using accelerated ageing by artificial acid rain. The degradation mechanisms of material structure and tracking resistance are discussed. The experimental results reported here show that the erosion of acid rain causes the degradation of the surface chemical and physical structures of polystyrene (PS) material so that the surface conductivity of aged material increases. Under electrical stress, the surface discharge current increases, and the local surface is deteriorated so that the tracking is initiated earlier and the material rapidly fails. The degradation rate of PS material in acid rain varies as function of the ion concentration, pH and conductivity of acid rain. Only the severe acid rain of high acidity and conductivity can exert an influence on PS insulating material. The concentration of actual rainwater is insufficient to lead to obvious erosion on PS insulation. PS insulation could resist on the erosion of normal acid rainwater. Even though clear degradation occurs with strong acid rain, PS could behave quite well in mild acid rain conditions.