Lignin-phenol-formaldehyde adhesives for exterior grade plywoods

Lignin-phenol-formaldehyde adhesives for plywood were prepared using lignin obtained by acetosolv delignification of Eucalyptus globulus wood. The formaldehyde/phenol mole ratio (F/P) was varied between 1•5 and 2•5, the soda/phenol mole ratio (S/P) between 0•4 and 0•6, and the percentage of substitution of phenol by lignin (%S) between 20 and 40%. The reactivity of the resins and the quality of the pine and eucalyptus plywoods manufactured with them increased with the F/P and S/P ratios and decreased with increasing %S.