Aluminum hybrid based on lignin from rice straw as a multifunctional additive for natural rubber composites with...

The rising growth of agricultural waste poses significant challenges to environmental sustainability, community health, and commercial stability. However, the development of multifunctional bio-based additives that simultaneously provide reinforcement and antioxidant performance in natural rubber (NR) composites remains limited. This study examines the potential of an aluminum (lignin/silica/fatty acid) hybrid (Al(LSF)), derived from rice straw black liquor, as a dual-functional additive with reinforcing and antioxidant properties in natural rubber (NR) composites. The Al(LSF) hybrid was analyzed by XRF, SEM-EDX, TEM, particle size analysis, and zeta potential measurements. Morphology, curing behavior, mechanical properties, and thermo-oxidative aging resistance of Al(LSF) in NR matrices were also investigated. Results showed that Al(LSF) exhibited nanoscale characteristics enabling uniform dispersion in the NR matrix. The incorporation of Al(LSF) (1-4 phr) improved curing properties, as evident by the decreased optimum curing time by approximately 18.3% as compared to TMQ/NR composites. Tensile strength of NR composites increased by approximately 45.4%, and elongation at break reduced by approximately 26.4% at 1 phr loading of Al(LSF) hybrid. The improvement in thermo-oxidative aging resistance of NR composites with Al(LSF) could be observed from th increased aging coefficient from 0.43 to 0.55 (approximately 27.9%). NR composites reinforced with Al(LSF) displayed better mechanical strength and aging properties than those filled with conventional fillers such as silica and sodium bentonite, depending on hybrid loading. Al(LSF)/NR composites can be explored for applications requiring improved long-term thermo-oxidative aging resistance and mechanical strength, such as tires, conveyor belts, gaskets, shoe soles, and other rubber products used outdoors exposed to extreme environmental conditions. Therefore, Al(LSF) hybrid could be considered as a potential multifunctional bio-additive to enhance mechanical strength and thermo-oxidative stability of NR while valorizing agricultural waste.