Synthesis and properties of resol-type phenol-formaldehyde resins prepared from H2SO4- and HCl-catalyzed phenol-liquefied Cryptomeria japonica wood

Wood of Cryptomeria japonica (Japanese cedar) was liquefied in phenol with H2SO4 or HCl as catalysts and used as raw materials to prepare phenol-formaldehyde (PF) resins. The curing behavior and adhesion properties of resins prepared were investigated. Wood liquefied with H2SO4 as a catalyst had better liquefaction effect than that with HCl; however, the reaction of resin synthesis was hard to control due to its quickly increasing viscosity. Differential scanning calorimetry analysis shows that PF resins prepared from HCl-catalyzed liquefied wood had higher reactivity than those of H2SO4-catalyzed wood. These PF resins were employed for manufacturing three-layer plywood. The wet bonding strength of plywood prepared with resins from HCl-catalyzed liquefied wood exceeded 0.7 MPa and fulfilled the requirement of the CNS 1349 standard.