Abstract: Liquefaction of walnut shell in phenol using sulfuric acid as catalyst was investigated under different conditions of mass ratio of phenol to walnut shell, dosage of catalyst, reaction time and temperature. Results showed that with the increasing of phenol/walnut shell ratio from 2/1 to 5/1, the amount of residue decreased from 26.49% to 6.60%. With dosage of catalyst from 2% to 4%, reaction time from 5 to 120 min and temperature from 100 to 150℃, the amounts of residue decreased from 20.79% to 10.48%, 48.84% to 15.62% and 28.86% to 9.39%, respectively; the contents of unreacted free phenol decreased from 17.32% to 12.67%,41.71% to 10.25% and 21.94% to 14.33%, respectively too. Weight average molecular weight (M_W) and degree of polydispersity of resultants of liquefaction decreased to 706-1 030, 1.04-1.25, respectively. The high-molecular weight part of liquefaction product decreased with increasing of phenol/walnut shell ratio, but increased with the increasing of H₂SO₄ concentration, reaction time and temperature. Compared to conventional phenol-formaldehyde (PF) resin adhesives, the liquefied walnut shell/phenol/formaldehyde co-condensed (WPF) resin can be used as adhesives for plywood with its bonding strength of 1.33 MPa.

Key words: walnut shell, phenol, liquefaction, resinification, wood adhesives