Nanocomposites of organophilic montmorillonite (C18-MMT), nitrile-butadiene rubber (NBR), and a coupling agent were produced during a melt compounding process at room temperature. During the process, it was clearly observed that organo-MMT particles were exfoliated into nanoscale layers of approximately 1-30 nm thickness, in addition to their original 40 mum thickness. These MMT layers were uniformly dispersed in the NBR matrix. The effects of a coupling agent such as 3-(mercaptopropyl)trimethoxy silane in C18-MMT/NBR nanocomposites were studied. The C18-MMT/NBR nanocomposites in the presence of the coupling agent were identified and characterized by X-ray diffraction, transmission electron microscopy, a universal testing machine, thermogravimetric analysis, and IR spectroscopy. It was observed that an additional silane coupling agent, 3-(mercaptopropyl)trimethoxy silane, enhanced the chemical interaction and was accompanied by the formation of Si-O-Si coupling bonds between C18-MMT and the coupling agent and Si-C coupling bonds between NBR and the coupling agent. This work resulted in improved properties of organo-MMT/NBR nanocomposites because of the nanoscale effects and strong interaction of the coupling bonds between NBR and organo-MMT. (C) 2003 Wiley Periodicals, Inc.