The effects of coupling agents on the mechanical properties of NBR-clay nanocomposites and its conventional composites

Organoclay, precisely montmorillonite, is modified with octadecylamine and then its surface is individually treated by silane coupling agents, DB550, DB580, and DB619. The nitrile butadiene rubber (NBR) is mechanically mixed with organophilic clay via melt blending method. Characterizations of prepared hybrids based on NBR-organoclay treated by silane coupling agents are investigated on such aspects as X-ray diffraction (XRD), scanning electron microscopy, infrared spectra, mechanical properties, and dynamic mechanical analysis (DMA). The XRD result shows that layered silicates are intercalated by polymer chains. The nanocomposites with coupling agent DB580 or DB619 have superior mechanical properties in comparison with conventional composites and ordinary nanocomposites. Apart from a limited increase in tensile stress at small strains, the ultimate stress at rupture of the nanocomposites is much higher than that of microcomposites. It is presumed that these enhancements are attributed not only to the more uniform dispersion of nanoparticles of organoclay into the polymer matrix but also to the coupling agent bond or micro-adhesion between the NBR matrix and the organoclay.