CURING CHARACTERISTICS AND ADHESION PERFORMANCE OF PHENOL-FORMALDEHYDE RESINS WITH COMPOSITE ADDITIVES

摘要

The curing characteristics of cure-accelerated phenol-formaldehyde resins with composite additives were investigated by differential scanning calorimetry analysis and gelation test. The pot lives and adhesion performances of phenol-formaldehyde resins were evaluated by viscosity variations and wet shear strength test of plywood respectively. Results indicated that the incorporation of triacetin and urea effectively accelerated the curing rate and improved the adhesion performances of phenol-formaldehyde resins with their pot lives for more than or equal to 8 hours. The individual triacetin-accelerated phenol-formaldehyde resin could fast cure at relatively low temperature with higher wet shear strength, but its pot life was less than 1 hour which was useless for the plywood industry. Urea as additive did not accelerate the curing rate of phenol-formaldehyde resin, but it was better at improving wet shear strength compared with control resin. At least 4 min were necessary for the wet shear strength of all specimens to reach 0.7 MPa required by the Chinese National Standard. Composite additive at 0.7% urea + 0.3% triacetin showed the best acceleration effects on curing process and wet shear strength of the phenol-formaldehyde resins and had suitable pot life for plywood production.