Softening Temperatures and Durability of Wood Adhesives

Thermal softening temperatures for six types of commonly used wood adhesives and some of their copolymers were examined. All melamine and phenolic resins, either dry or moist, gave softening temperatures greater than 120°C at 9°C/min. heating rate, while urea resin softened at temperatures less than 70°C. The softening temperature of urea melamine resin increased with increasing content of melamine. Casein glue exhibited a greater softening temperature (80°C) when dry than urea resin, but its softening temperature decreased linearly with increase of moisture content. The durability ranking of the same adhesives was found to be consistent with the ranking by softening temperature.