Effect of Lignin Structure Characteristics on the Performance of Lignin Based Phenol Formaldehyde Adhesives.

As the second most abundant biopolymer, lignin remains underutilized in various industrial applications. Various forms of lignin generating from different methods affect its physical and chemical properties to a certain extent. To promote the broader commercial utilization of currently available industrial lignins, lignin sulfonate (SL), kraft lignin (KL) and organosolv lignin (OL) were utilized to partially replace phenol in the synthesis of phenol formaldehyde (PF) adhesives. The impact of lignin production process on the effectiveness of lignin-based phenolic (LPF) adhesives was examined based on the structural analysis of the selected industrial lignin. The results showed that OL had more phenolic hydroxyl groups, lower molecular weight and greater number of reactive sites than the other two types of lignins. The maximum replacement rate of phenol by OL reached 70% (w/w), resulting in organosolv lignin phenolic (OLPF) adhesives with a viscosity of 960 mPa·s, a minimal free formaldehyde content of 0.157%, and a shear strength of 1.84 MPa. It exhibited better performance compared with the other two types of lignin-based adhesives and met the requirements of national standards. This article is protected by copyright. All rights reserved.