Characterization of Engineering Wood Adhesive Behavior Treated at Elevated Temperatures

Shi, S., Oppedal, A. L., Miller, G., & Horstemeyer, M. (2005). Characterization of Engineering Wood Adhesive Behavior Treated at Elevated Temperatures. In C. R. Frihart (Ed.), Wood Adhesives 2005. San Diego, CA: Forest Products Society. 163-169.

The objective of this research was to investigate the effect of elevated temperatures on the surface mechanical properties of resin films prepared from adhesives commonly used in engineered wood products. Three commonly-used engineering adhesive types were evaluated: phenol-resorcinol-formaldehyde (PRF), melamine-ureaformaldehyde (MUF), and polyurethane (PUR). The cured adhesive resin films were prepared and subjected to temperature treatments at 100°, 150°, 200°, 250°, and 300°C for 5, 30, and 60 minutes. Nanoindentation technique was used to characterize the modulus and hardness properties of the resin films treated at different temperatures up to 200°C. Block shear tests were also conducted in accordance with the principles described in (1) after the specimens were treated at different elevated temperatures. This research showed that the nanoindentation technique was a good tool to characterize the mechanical properties of the cured adhesive resin films. For all three adhesive types evaluated, the structures of cured resin samples were subjected to significant change after a heat treatment at 250°C and above. Based on the nanoindentation test results, the behaviors among the three adhesive types were totally different in response to temperature. For the PRF resin, both modulus and hardness increased linearly as a function of temperature up to 200°C. For the PUR resin, the modulus and hardness first decreased when the temperature increased from room temperature to 100°C, and then increased as the temperature continued to increase to 200°C. For the MUF resin, the modulus and hardness increased as a function of temperature up to 150°C and dropped at 200°C. A strong relationship was found between the reduced modulus and hardness on the adhesive resin films from the nanoindentation tests.