Organosolv lignin in phenol formaldehyde resins : evaluation of curing behaviour and wood bonding effectiveness

Softwood kraft lignin (KL) and hardwood organosolv lignins (OL) from ethanol-water pulping were characterized by functional group analysis, molecular weight distribution and thermal analysis. The properties of lignin-phenol-formaldehyde resins (LPF), synthesized with these lignins were evaluated and the performance was measured by thermal analysis of the curing process. The wood bonding effectiveness was tested in an Automated Bonding Evaluation System (ABES). All resins formulated were compared to a pure PF resin. The results indicate that the high molecular weight, high purity organosolv lignin shows a high potential for application in wood adhesives. Shear strength of this OL-based PF resin is comparable with strength values of the neat resin.