Processing rheological behavior of functionalized silica/natural rubber composites

The filler networks of natural rubber (NR) silica-filled coupling agents KH560, Si69, and NXT were studied using a rubber processing analyzer (RPA). The effects of different coupling agents on the rheological behavior of silica-filled NR were investigated. The results showed that the three types of coupling agents could control the surface properties of silica, diminish the silica network, reduce the storage modulus and loss modulus, weaken the Payne effect, and improve processability. A comprehensive modification effect was observed for the coupling agent NXT. For different modified silica loading scenarios, the rheological properties of natural rubber composites filled with silica modified by the silane coupling agent NXT were assessed. The Payne effects were more obvious with the increased loading of fillers, while G' and G″ nonlinearly rose with the increase of frequency. Finally, the platform effect appeared, demonstrating the shear thinning phenomenon. The best compatibility and minimum extent of agglomeration of silica was obtained from the composite filled with 50 phr silica.