Imidazolium ionic liquid compatibilizers in melt-blended styrene-butadiene rubber/aramid pulp composites

Carbon black (CB) is commonly used as filler in the rubber industry, although it is potentially polluting and its production demands high energy. It would be beneficial if other fillers could replace CB, even if only partially. Aramid fibers have been used in a range of applications in the rubber industry; however, their relatively inert surface is an obstacle for obtaining composites with enhanced properties. In this work, three ionic liquids were investigated as compatibilizers in the preparation of styrene-butadiene rubber composites with aramid pulp, which were characterized using swelling, hardness, and tensile tests, differential scanning calorimetry, thermogravimetric, and infrared spectroscopy analyses, as well as scanning electron microscopy. The ionic liquid-treated aramid pulp showed higher degree of fibrillation, and the composite with 5 phr of aramid pulp containing 0.5 wt.% of physisorbed ionic liquid showed the highest increment in tensile strength, ca. 42% superior to the IL-free composite, confirming the potential of imidazolium ionic liquids to act as compatibilizers and greatly outperforming related previous work due to differences in the composite preparation techniques.