In this work, a novel environmentally friendly lignin-based adhesive crosslinked with a furfuryl alcohol–glyoxal resin and epoxy resin (EPR) was used to bond particleboard. The results of ¹³C nuclear magnetic resonance and matrix-assisted laser desorption–ionization time-of-flight mass spectroscopy indicated that furfuryl alcohol and glyoxal reacted under acidic conditions and that–CH–(OH)–groups may be involved in the crosslinking of the lignin–furfuryl–glyoxal resin, which also easily crosslinked with EPR. The IB strength of the particleboard bonded with LFG + 9 % EPR adhesive was better than that of the particleboard bonded with lignin–furfuryl alcohol (LF) adhesive. Moreover, the modulus of elasticity of the LFG + 9 % EPR adhesive was higher than that of the LF and phenol-formaldehyde adhesives.

By focusing on the disadvantages of weak water resistance and high formaldehyde emission of urea–formaldehyde resin (UF), this research provides a new method to overcome these shortages of UF resin by using tannin for partial substitution of urea. Furthermore, plasma pretreatment of wood was introduced to strengthen the bonding performance of plywood. The investigation of the chemical structure of UF resin and tannin–urea–formaldehyde resin (TUF) were performed with Fourier transform infrared spectroscopy (FT-IR) and solid-state ¹³C nuclear magnetic resonance (¹³C NMR). The results of investigations confirmed the joining of tannin into the resin structure, which may enhance structural rigidity of TUF adhesives and improve hydrolysis stability. Then, thermal performance of UF resin and TUF resins were tested by differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis. The DSC results indicated that the curing temperature did not change significantly. However, the TG analysis showed that the thermal stability of TUF resin was considerably improved. In bonding performance test, tannin–urea–formaldehyde resin (TUF) revealed an excellent water resistance, comparable to UF resin and can fulfill the standard requirement for plywood (Type II according to the Norm GB/T 17657-2013). It is interesting that the shear strength of wood specimens, bonded with TUF6 resin, after low-pressure cold plasma equipment (CLP plasma) and jet type atmospheric low-temperature plasma (JTLP plasma) treatment, reached 0.80 MPa and 0.85 MPa, respectively, after being soaked in boiling water for 3 h. In addition, most of the bonded plywood samples with TUF resin exhibited a lower formaldehyde emission, especially those prepared at 70 °C and 1.5 h, in which the formaldehyde emission amount could be reduced by approximately 39%.