• polysiloxanes;
  • nanocomposites;
  • organoclay;
  • mechanical properties;
  • structure-property relations


Composites of silicone rubber reinforced with organomontmorillonite (OMMT) nanoparticles were prepared by direct mixing and characterized in terms of morphology, in correlation with mechanical performance. Two grades of commercial montmorillonite (MMT) with different types of organic modification were studied, namely Cloisite® 20A and Cloisite® 30B. Low, medium, and higher molecular weight PDMS were used as matrices. Using X-ray diffraction analysis, it was shown that OMMT loadings at a weight ratio to resin ranging from 5 to 10 parts per hundred (phr) can produce delamination hybrids. Mechanical testing showed that for OMMT loadings up to 8 phr, the prepared nanocomposites present higher tensile strength, stiffness, and tear resistance with respect to the neat silicone. Improvement of the solvent resistance was also recorded by swelling experiments in toluene, and this behavior of the nanocomposites is consistent with their mechanical properties. The results showed that processing characteristics, as well as the overall reinforcing efficiency of nanofillers, are greatly dependent on the initial molecular weight of the elastomer, because this parameter controls the resulting network density and concentration of polar end groups. The content of organic modification of MMT was also found as an important characteristic for proper filler dispersion. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012