Organoclay-natural rubber nanocomposites synthesized by mechanical and solution mixing method

This investigation describes two methods to obtain rubber composites based on natural rubber (NR) and organophilic layered silicates. In order to improve the exfoliation and compatibilization of the organoclays with the rubber matrix, a new approach which involves swelling of the organoclays with an elastomer solution prior to compounding has been used. The effect of the addition during swelling of a coupling agent, namely bis(trietoxysilylpropyl)tetrasulfan (TESPT), on the behaviour of the composites was also investigated. The results show that a low amount of organoclay (10 phr) significantly improves the properties of natural rubber. This suggests a strong rubber-organoclay interaction which is attributed to a high degree of rubber intercalation into the nanosilicate galleries, as was confirmed from X-ray diffraction. In addition, an ulterior improvement in the properties of the nanocomposites prepared by solution mixing is clearly observed, due to the better filler-rubber compatibility. An even further increase in the properties is observed by treating the silicate with a silane coupling agent. The silane functional groups modify the clay surface, thus reducing the surface energy, and consequently improving the compatibility with the rubber matrix. (C) 2004 Society of Chemical Industry.