Recent concerns regarding the hazard potential of formaldehyde has led to the development and use of new formaldehyde-based resins that provide wood-based panels with significantly reduced formaldehyde emissions. Normal reliability testing using some of the typical analyses used for characterization of these low-emission resins, such as reactivity or tack methods, suffers from their reduced formaldehyde content. In this paper we introduce updated methods for resin characterization to overcome the above-mentioned deficits. The traditional gel time measurements are very subjective and the new low mole-ratio resins exhibit a difficult to judge end-point. Given the importance of resin cure time, a preferred method would be to monitor the curing process by a rheometer or a pH measurement with fast temperature adjustment. Nano-indentation tests of cured gluelines give valuable information on elasticity and hardness of the resin. We will also describe a new method that can accurately monitor the drying out behavior of resin systems and allow judgments on stickiness and tack properties of a resin.
展开▼
