The MOEs and MORs of seven-layer plywoods bonded with FPL, ureaformaldehyde and phenolformaldehyde resin adhesives. The dot-dashed lines at 5,500 MPa and 32 MPa mark the minimum industrial requirements for the MOE and MOR, respectively. Lignin adhesive preparation: 1:4 (w/w) lignin (or ureaformaldehyde or phenolformaldehyde)/water 1:4, pH 2.1 (except as indicated); hot-pressing pressure: 2.0 MPa. All examined moduli were found to be significantly (ANOVA, P < 0.01) affected by hot-pressing temperature, time and pH but not the glue application level (Extended Data Table 1 ). Error bars show the s.d. of measured bonding strengths with four repeats.
