木质素磺酸钠-壳聚糖基木材胶黏剂的合成、结构与性能OA

To improve the water resistance of lignin-based wood adhesives,the lignin sulfonate/chitosan(L/C)resin using lignin sulfonate(L)and chitosan(C)as raw materials under acidic conditions with different mass ratios,and high-activity isocyanate(MDI)was added as a crosslinking agent by blending towards the wood adhesive.The structure was then analyzed via Fourier-transform infrared spectroscopy(FT-IR)and X-ray photoelectron spectroscopy(XPS).Hydrophobicity was assessed through water contact angle tests,while curing performance was characterized by differential scanning calorimetry(DSC)and scanning electron microscopy(SEM).Next,the L/C resin blending with MDI was employed to prepare plywood,and its mechanical properties were tested.The results showed that the L/C resin primarily contained functional groups such as C—C,C=O,C—N,S=O,and S—N.The carbonyl and sulfonic groups in lignin sulfonate reacted with the amino groups in chitosan to form amide and sulfonamide bonds.The interaction between lignin sulfonate and chitosan through these bonds formed a more compact three-dimensional network structure,thereby improving the bonding performance and water resistance of the L/C resin.When the mass ratio of lignin sulfonate to chitosan(R)was 3∶1,the water contact angle of the L/C resin reached a maximum of 80°.Moreover,the L/C resin synthesized under these conditions of that R was 3∶1,the reaction temperature was 80℃,the reaction time was 30 minutes with the addition of 3%MDI crosslinking agent,showed the optimal performance in plywood.The dry shear strength,wet shear strength after 24 h cold water immersion,and wet shear strength after 3 h of 63℃hot water immersion were 1.22,1.09,and 0.78 MPa,respectively,meeting the strength requirements for Class Ⅱ plywood as per national standard GB/T 9846-2015.