Improving Dispersion of Alkali Lignin in Natural Rubber by Adopting Graphene Oxide as a Carrier

The sterically hindered phenolic groups in lignin make it suitable as an antioxidant in natural rubber (NR) composites. However, the large number of polar functional groups in lignin particles makes them prone to aggregation, resulting in poor dispersion in the NR matrix and thus reducing the properties of rubber composites. In the present study, an alkali lignin (AL)/graphene oxide (GO) composite suspension was prepared by using lamellar GO as the carrier of AL. The GO/AL/NR composite was then prepared by the latex coprecipitation method, with the GO/AL composite replacing 50 wt % of carbon black. The influence of the AL proportion on the properties of GO/AL/NR composites was studied. Micromorphology analysis showed that the dispersion of AL was significantly improved by introducing the GO carrier. When the mass ratio of GO to AL was 1:9, the "Payne effect" of the rubber composite was weakest. Compared with the original carbon black-filled NR composite, the tensile strength retention rate of GO/AL/NR composites containing a GO/AL (1:9) composite, which replaced 50 wt % of carbon black, increased by 14.5%, and the retention rate of elongation at break increased by 15.9%. Despite a 9.3% decrease in tensile strength (26.2 MPa), the composite demonstrated good antioxidant and mechanical properties.