CURING PROPERTY AND PLYWOOD ADHESIVE PERFORMANCE OF RESOL-TYPE PHENOL-UREA-FORMALDEHYDE COCONDENSED RESINS

The curing processes and thermal properties of resol-type phenol-urea- formaldehyde cocondensed resins, which were prepared by alkaline treat ments of the cocondensed resins once synthesized from UF-concentrate a nd phenol, were investigated by torsional braid analysis. The resol-ty pe cocondensed resins displayed almost the same curing behaviors and h eat-resistance as a commercial resol. Their apparent activation energi es determined by measuring temperature dependence of gel time were alm ost identical with that of resol, and quite different from that of UF resin. Their plywood adhesive performances were evaluated with a cycli c 4-hour boil test and a 72 hour boil test. The plywood test results p assed the requirements for the JAS special grade structural plywood.