Investigation into the effects of environmental stresses on RTV-1 silicone-based caulk materials

Single component room temperature vulcanized (RTV-1) caulks are used in a variety of electrical and other applications. In high voltage Non Ceramic Insulators (NCIs) they are used as part of a triple seal system near the metal end-fittings to protect insulators against environmental stressors including moisture and acid ingress and salt contamination. In service they must resist chemical aging for long periods of time. MacLean Power Systems, Inc. provided three RTV-1 caulk materials for evaluation, of which all three materials maintained their hydrophobicity or increased their hydrophobicity during acid immersion and UV/condensation tests. However, all three materials showed significant mass and hydrophobicity loss upon exposure to salt water at elevated temperatures. Our results show that RTV-1 materials perform differently when compared to Silicon Rubber (SIR) insulator shed materials as reported in the literature when exposed to acid immersion. This is due to the absence of aluminum hydroxide in RTV-1, also referred to as aluminum trihydrate (ATH). Additional acid immersion testing was conducted with ATH resulting in depolymerization of the RTV-1 material.