Mechanochemical\nMethacrylation of Lignin for Biobased\nReinforcing Filler in Rubber Compounds

The inclusion of biobased materials as fillers for rubber\ncompounds\nis an emerging topic in the tire industry. This study investigates\nthe use of kraft lignin, a byproduct of the paper industry, as an\nalternative reinforcing filler for rubber compounds. Methacrylation\nof lignin was achieved through mechanochemistry, resulting in an estimated\nfunctionalization degree of 22% for aliphatic and 17% for phenolic\nhydroxyl groups. The modified lignin was predispersed in natural rubber\nvia coprecipitation with a natural rubber latex. The reinforcing effect\nof lignin was tested in model tread and sidewall compounds by using\neither a sulfur or peroxide vulcanization system. Dynamic mechanical\ntests revealed that methacrylated lignin enhances compatibilization,\ndispersion, and stiffness within the elastomeric matrix more effectively\nthan unmodified lignin due to covalent bond formation during vulcanization.\nIn peroxide-cured composites, functionalized lignin combined with\nsilica exhibited a higher storage modulus and lower hysteresis compared\nto unmodified lignin, suggesting potential for designing fuel-efficient\ntires.