High molar mass silicone rubber reinforced with montmorillonite clay masterbatches: Morphology and mechanical properties

Rubber composites were obtained from natural (MT) or organomodified (O-MT) montmorillonite clay masterbatches and high molar mass poly(dimethylsiloxane)-gum (PDMS). The masterbatches were prepared by compounding MT or O-MT with a siloxane–polyether surfactant. The rubber composites were characterized by X-ray diffraction, small angle/wide angle X-ray scattering, scanning and transmission electron microscopies and tensile tests. The results showed that masterbatch compounding with O-MT improved the dispersion of this clay into the PDMS matrix. The morphology of the resulting composite showed a combination of intercalated and partially exfoliated clay layers with occasional clay aggregates. The addition of only 5 phr of O-MT into the PDMS matrix, via masterbatch compounding, improved the tensile strength as much as that obtained with the composite filled with 30 phr of O-MT clay prepared by the direct addition of the clay to PDMS. Moreover, the elongation at break was improved by at least 126%.