Abstract
We have investigated the relation between the molecular weight distribution (MWD) of diffusible species and the recovery rate of hydrophobicity of room-temperature vulcanizing (RTV) silicone rubber (SIR) using solvent extraction at various temperatures. Using gel permeation chromatography (GPC), we confirmed that the extract had a MWD ranging from a few hundreds to hundreds of thousands, and the average molecular weight (MW) of the extract having MW over 3000 increased with the increase of extraction temperature. By measuring the infrared (IR) absorption of siloxane migrating to the extracted SIR surface through a thin carbon coating, the aspect of migration of diffusible species was observed as a real time plot, and the time constant of the migration was calculated. According to the time dependence of IR-absorbance, the time constant was increased with the increase of MW of the extracts. It was found that the recovery rate of hydrophobicity of SIR was related to the MWD of the diffusible species.
