GMA-functionalized alkali lignin that can be covalently cross-linked is used in NR sustainable tire composites

Alkali-lignin (AL) is a commonly used biomass filler in natural rubber (NR) due to its abundant yield and aromatic structure. However, its compatibility with NR at the nanoscale is challenging due to its inherent polarity. In this study, glycidyl methacrylate (GMA) was used to modify AL to prepare modified alkali lignin (ALG), which introduced a polymerizable CC bond and reduced the polarity of AL. DFT (Density Functional Theory) results confirmed that the binding energy of NR/ALG was 2.57 % higher than that of NR/AL, and the compatibility was significantly improved. ALG can be dispersed with natural rubber latex at the nanoscale in aqueous solution. At the same time, ALG could photopolymerize with NR under UV light to form a wide range of lignin/NR cross-linking networks, which were further strengthened during the vulcanization process to achieve multiple enhancement effects. The tensile strength of NR@ALG reached 30.98 MPa, 27.9 % higher than that of pure NR. When co-doped with CB, NR@ALG@C has a higher tensile strength of 32.1 MPa, which is 13 % higher than that of NR@C. In addition, ALG also promoted the dispersion of CB in NR, and the particle size of NR@ALG@C decreased by 22.2 % compared with that of NR@C. The high E 'value in the DMA dynamic temperature scan further demonstrates the stability of the covalent structural network inside the composite. This environmental protection strategy successfully realizes the high-value utilization of industrial lignin, converting it into high-performance rubber composite fillers that are highly compatible with the goals of the circular economy.