On the responsiveness of hardened UF-resins of different molar ratio towards ammonia fumigation

Fumigation of two cross-linked UF-resins of molar ratio U:F 1:2.1 and 1:1.4 with ammonia reduces their formaldehyde release. The reduction seems to be more excessive in case of resin with molar ratio U:F 1:2.1. Ammonia fumigation also increases the nitrogen content of the hardened resins depending on their molar ratio U:F. Resin of the molar ratio U:F 1:2.1 is more receptive to ammonia than that of U:F 1:1.4. Moreover, the pH-value of aqueous extractives of the resins increases due to the ammonia treatment depending on the molar ratio U:F of the resin. Resins with high formaldehyde content are more responsive to ammonia fumigation.