Black Liquor as a Multifunctional Additive for Enhancing Mechanical and Antioxidant Properties of Natural Rubber Latex

ABSTRACT The black liquor (B)L produced in the alkaline pulping process of the paper industry is currently mainly used as fuel, which has low utilization efficiency and causes significant environmental pollution. This study leverages the alkaline nature of BL, which easily mixes with natural rubber latex (NRL), and the antioxidant properties of its main component, lignin, to use it as an additive in NRL, enhancing the strength and antiaging properties of rubber latex products and compares it with commercial lignin. The research results indicate that BL can reduce the viscosity of NRL and enhance its mechanical and thermal stability, which is beneficial for the processing of NRL products. BL improves the mechanical and antioxidant properties of NRL films, outperforming commercial lignin in both reinforcement and antioxidant effects. With the addition of 1.25 phr BL, the tensile strength and tear strength of the vulcanized rubber latex film are enhanced by 46.74% and 36.47%, respectively, compared to NRL film and by 15.79% and 12.16% compared to commercial lignin. This paper not only provides insights into the green and high‐value utilization of BL but also offers new methods for exploring eco‐friendly additives for NRL.