Rubber nanocomposites based on compatibilized NBR/SBR blends using a series of amphiphilic montmorillonites

The montmorillonite (MMT), Mont-0, was treated with different levels of appropriate corresponding amounts of cetyltrimethylammonium bromide to yield a variety of biphasic MMTs exhibiting different hydrophilic–lipophilic balance ranging gradually up to the highly hydrophobic form (Mont-100), which was proved using Fourier transform infrared spectra as well as x-ray diffraction, thus the produced forms can be arranged in the following order according to the decrease in hydrophilicity: Mont-0 > Mont-25 > Mont-50 > Mont-75 > Mont-100. In a following step, the obtained MMTs were attempted for use as reinforcing fillers that may exhibit in the mean time a compatibilizing effect, for acrylonitrile–butadiene rubber (NBR)/styrene–butadiene rubber (SBR) (50/50) rubber blend, which is known to be physically incompatible. The mechanical performance of the blends comprising different loadings of MMT forms demonstrated advancement in most of the cases accompanied by acceleration in rheometric characteristics indicating enhancement by different extents in compatibility between the phases. The results were explained on the light of the potential of these MMT forms to bind both phases of the blend through hydrophobic–hydrophobic interactions with the nonpolar part (SBR) and polar–polar interactions with the polar part (NBR) of the blend, which diminishes the molecular mobility of the macromolecular chains thus preventing progress in phase separation. These findings were additionally proved using scanning electron microscopy and XRD that confirmed a dependent contribution of both phases in interfacial interactions with the biphasic fillers as a function of the hydrophobization level.