Effect of surface modified montmorillonite on photo-oxidative degradation of silicone rubber composites

Abstract

Basal spacing of montmorillonite (MMT) was improved through a column chromatography technique using quaternary long chain ammonium salt as an intercalent. An increase in d-spacing of organic montmorillonite (OMMT) was confirmed by XRD and found to increase from 16 to 22 A. The d-spacing was maximum (22 A) due to an ion exchange column of sufficient length (35 cm) and diameter (5 cm), which provides maximum retention time for the proper exchange of ions between plates of MMT and ion exchange resin packed into the column. Nanocomposites (OMMT: silicone rubber) were prepared using a solution blending method. The material was compounded on a two roll mill and molded in a compression molding machine in order to obtain a square (0.2 mm thickness) sheet. Photo-oxidative degradation of OMMT: silicone rubber composite was studied under accelerated UV irradiation (≥290 nm) at different time intervals. Prolonged exposure to UV leads to a progressive decrease in mechanical and physical properties along with the change in behavior of the filler-matrix interaction, which was due to decrease in cross-linkage density with an increase in the mobility of rubber chains. The increase in carbonyl (>CO), hydroxyl (-OH) functional groups on irradiation of OMMT: silicone rubber composites at different time intervals were studied using Fourier transform-infrared spectroscopy (FTIR). Whereas, change in morphological behavior regarding the OMMT-matrix interaction on irradiation was studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Overall, the study showed that the OMMT: silicone composites were affected more on irradiation than pristine silicone composites.