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Sodium lignosulfonate amine (SLA) was synthesized by Mannich reaction. The lignin-modified waterborne polyurethane (WPU) with different branched structures was designed and prepared by introducing SLA as a hydrophilic chain extender. The effect of the introduction manner of SLA on the performance of WPU was systematically investigated. The results showed that the addition of 0.75 wt% SLA in an appropriate introduction manner can prepare a polyurethane dispersion with good stability and high solid content. The tensile strength of the SLA-modified WPU film was significantly improved to 37.3 MPa. The SLA-modified WPU film also exhibited high water resistance and thermal stability. Moreover, in the introduction manner of WPU-C, the adhesive properties of SLA-modified WPU adhesives were also improved, which was mainly attributed to the entanglement of long branched chains generated by SLA chain extension with other polyurethane chains and the formation of physically cross-linked networks through the interaction between functional groups. Therefore, the introduction of a small amount of sodium lignosulfonate amine in an appropriate manner can significantly improve the performance of WPU with high solid content, which provides a new way to prepare high-performance waterborne polyurethane. [Display omitted] • Sodium lignosulfonate amine optimized the structure of waterborne polyurethane. • A small amount of sodium lignosulfonate amine improved the properties of WPU. • Provide a new idea for preparation of high-performance WPU. • Expand the way for high-value utilization of sodium lignosulfonate. [ABSTRACT FROM AUTHOR]