Curing of low level melamine-modified urea-formaldehyde particleboard binder resins studied with dynamic mechanical analysis (DMA)

Effects of resin formulation, catalyst, and curing temperature were studied for particleboard binder-type urea-formaldehyde (UF) and 6 similar to 12%, melamine-modified urea-melamine-formaldehyde (UMF) resins using the dynamic mechanical analysis method at 125 - 160 degrees C. In general, the JF and UMF resins gelled and, after a relatively Iona low modulus period, rapidly vitrified. The gel times shortened a the catalyst level and resin mix time increased. The cure slope of the vitrification stage decreased as the catalyst mix time increased, perhaps because of the deleterious effects of polymer advancements incurred before curing. For UMF resins, the higher extent of polymerization effected for UF base resin in resin synthesis increased the cure slope of vitrification. The cure times taken to reach the vitrification were longer for UMF resins than UF resins and increased with increased melamine levels. The thermal stability and rigidity of cured UMF resins were higher than those of UF resins and also higher for resins with higher melamine levels, to indicate the possibility of bonding particle-board with improved bond strength and lower formaldehyde emission. (c) 2005 Wiley Periodicals, Inc.