Fabrication of oxidized lignocellulosic nanofibers to realize NR composites with high reinforcement, photothermal properties and intrinsic aging resistance.

Developing nano-polysaccharides as the reinforcing fillers and antioxidants for natural rubber (NR) composites is critical for addressing environmental and sustainability concerns. However, the aggregation of nano-polysaccharides within the NR matrix hinders their potential application. Herein, oxidized lignocellulose was prepared using hydrogen peroxide and copper ions, followed by high-pressure homogenization to produce oxidized lignocellulosic nanofibers (OLCNF). Oxidation introduced carboxyl groups that partially ionized to -COO- upon aqueous homogenization, generating electrostatic repulsion which facilitated nanofiber exfoliation and prevented re-aggregation. When 50 phr OLCNF was incorporated into NR latex, the NR/OLCNF-50 exhibited a 100% modulus of 7.2 MPa. This 5-fold improvement over NR is attributed to residual lignin in OLCNF, which enhances interfacial compatibility between the matrix and the fillers. Notably, under simulated sunlight irradiation, the surface temperature of NR/OLCNF-50 rapidly increases to 140.0 °C generates thermoelectric output of 290 mV and 36 mA, with robust deicing ability, meanwhile. Strikingly, the carboxyl groups in OLCNF improve the accessibility of hydroxyl groups and enhance intrinsic-antioxidant efficiency, enabling the scavenging of 79.4% of 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH) at 2 mg/mL. After 48 h of thermal aging at 100 °C, NR/OLCNF-50/no-6PPD shows only 25.8% loss in elongation at break. Consequently, this green processing method provides a sustainable pathway for developing high-performance NR composites with high intrinsic-antioxidant efficiency and photothermal conversion.