Effect of walnut-shell filler as sustainable material with silane to replace carbon black in natural rubber-based tire tread compound

In this paper, walnut shell filler of 75–150 µm and 45–75 µm size was used in rubber compound with different loadings (2,3, and 5 phr). At 2, 3, and 5 phr loading, small-size WNS powder (45–75 µm) has higher modulus at 300%, tensile strength and elongation at break than larger-size powder (75–150 µm); however, modulus at 300% is lower than blank compound. As the amount of WNS filler increases, the elongation at break with modulus at 300% and tensile strength decrease. The goal of using silane is to improve the interfacial interaction between WNS filler and the rubber matrix. Larger-size WNS filler using Si69 compound demonstrated higher modulus at 300% with higher elongation at break and tensile strength compared to non-silanised compound; however, modulus at 300% remained lower than blank compound. The silanised compound with both WNS fillers demonstrated slightly higher rebound resilience at 100 °C, slightly lower heat build-up, and slightly lower tan delta at 60 °C than the blank compound. It was demonstrated that small-size WNS filler with silane could partially replace N330 carbon black (3 phr) in natural rubber-based tire tread compound due to its bio-based, biodegradable, renewable and sustainable properties.