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A lignin-based PU coating was prepared for paper-based green packaging. Two representative diisocyanate were used to prepare the coatings. Due to the rigid aromatic, the physical properties of the TDI system reached the maximum below the lignin content of 40%. The HDI that contains flexible aliphatic chains alleviated the brittleness of coating, and it showed physical advantages when the lignin content was more than 50%. Owing to the high lignin content, the coating presented enhanced thermal stability. After coated with the lignin-based PU coatings, the dry tensile strength of coated paper was improved by 126%. Amazingly, the wet strength was increased from 0.31 to 12.6 MPa with an improvement nearly 40 times. Based on the coordination of lignin, Ag+ was introduced into the PU matrix, which imparted the coating with excellent antibacterial ability. The colony forming units of E. coli and S. aureus were both less than 1. However, no inhibition halo was observed, which indicated that the Ag was firmly anchored on the coating and the antibacterial ability is only available when the bacterial contact the coating surface. The lignin-based PU coating with favorable sustainability and properties shows great potential in paper-based green packaging fields. The prepared PU coating with high lignin content and firmly anchored Ag+ exhibits outstanding physical properties, thermal stability, and antibacterial property, which makes it an ideal candidate to be used in paper-based green packaging. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel dimer acid-based waterborne polyurethanes (DWPUs) were designed and prepared. • DWPUs were first used as multifunctional coatings for paper substrates. • Papers coated by DWPUs exhibited excellent water- and oil-resistances. • Alkyl and uniform membrane of DWPUs are critical to improve papers' properties. Paper derived from lignocellulose has great advantages over plastics as packaging material, nevertheless, the poor water- and oil-resistances of paper-derived products limited their application in high-end field. Herein, novel dimer acid-based waterborne polyurethanes (DWPUs) with different content of dimer acid-based polyester polyol (DG) were prepared and used as water- and oil-resistant coating for paper substrate. The effects of DG contents on water- and oil-resistances, mechanical properties and thermal stability of DWPUs coated papers were systematically investigated. When the content of DG reached up to 7 wt% (based on polyester glycol), the paper coated by DWPU exhibited 88.06% decrease in Cobb 60 value, 8.7 times increase in kit rating compared with uncoated paper. Meanwhile, DWPUs coated papers showed good mechanical properties and thermal stability. These improvements are attributed to the flexible long-alkyl chain, and six-ring structure of DWPUs as well as the continuous and homogeneous DWPU-derived membrane on the surface of paper. This study provides a new framework for the preparation of high quality, multifunctional, environmentally friendly water- and oil-resistant coatings for paper substrates. [ABSTRACT FROM AUTHOR]