Improving the properties of phenol-lignin-glyoxal as a wood adhesive by lignin nanoparticles

The present study provides a new concept for improving the properties of phenol-lignin-glyoxal (PLG) resins by lignin nanoparticles, a bio-nanomaterial. In the research work presented, lignin nanoparticles (10, 20, 30 and 40 wt%) were used instead of lignin for the phenol-lignin-glyoxal resin synthesis. The physicochemical and thermal properties of the prepared resins were then determined as well as the water absorption and mechanical properties (flexural modulus, flexural strength and internal bonding) of the particleboard panels bonded with them according to related standards methods. The addition of lignin nanoparticles appeared to change the physicochemical properties of the resins as the gelation time of the PLG resin was shorter and its viscosity increased. FTIR analysis indicated no differences in the chemical structure between the PLG resins with lignin and nanolignin. DSC analysis shows that the addition of lignin nanoparticles allows to decrease the curing temperature of the PLG resin from 170 °C to 159 °C. Based on panel analysis results, higher mechanical strength values and lower water absorption were obtained by progressively increasing the lignin nanoparticles proportion. The work presented here provides a new concept for the preparation of phenolic resins.