Achieving High Strength, Toughness, and Low Heat-Buildup in Natural Rubber Composites: An Interfacial Design with Inverse Vulcanized Copolymer-Modified Silica

Based on an inverse vulcanization polymerization strategy, this study developed an interfacial modifier, sulfur-1-octadecene copolymer (SPO), by integrating nonionic surfactant modification with an inverse vulcanization synthesis process. SPO was designed to simultaneously address two major challenges in SiO 2 (silica)-filled natural rubber (NR) composites: poor filler dispersion and high volatile organic compound (VOC) emissions. The SPO molecule contains multiple amine groups and polysulfide bonds, enabling a dual interfacial bonding mechanism via synergistic hydrogen bonding and covalent interactions within the SiO 2 /NR composite. This mechanism significantly enhances both the dispersion of SiO 2 in the rubber matrix and interfacial adhesion. Compared to composites modified with the conventional silane coupling agent Si69, the SPO-modified SiO 2 /NR composite demonstrates superior overall performance: its tensile strength increases to 29.6 MPa with an elongation at break of 669%. The dynamic mechanical properties are also markedly improved, showing a 15.6% reduction in the Payne effect (Δ G ′) and a 8.4% decrease in the loss factor (tan δ). This indicates a lower tendency for heat buildup and a lower energy-dissipation efficiency (EDE) than the Si69-modified counterpart. Furthermore, the SPO modification process avoids silanization reactions, eliminates VOC emissions, and improves vulcanization efficiency. This inverse vulcanization approach provides a high-value application for the large amounts of waste sulfur generated by the petroleum industry. This study offers a green and sustainable pathway for designing high-performance, low-hysteresis rubber composites for use in the field of green tires.