Wood Adhesives Science and Technology
FS-FPL-4703

Research Summaries

Summaries of research areas that the group has recently been working on:

Problem 1 – It is important to understand where and why the adhesive bond fails under accelerated tests to determine if such results relate to in-service performance. Using a variety of refined analytical techniques, our studies on epoxy adhesives show that the failure is more in the epoxy interphase layer than it is at the interface or in the wood interphase layer. When wood is wet, one way to reduce the swelling effect is to use acetylate wood. Past work has shown that only some adhesives bond well to acetylated wood. Current data shows that epoxies bond well to acetylated wood even under wet conditions if the wood is not planed after acetylation, but fail when used to bond untreated or acetylated-treated wood that has been freshly planed. These studies have led to both a new theory as to why wood bonds fail when exposed to wide moisture cycles and to development of improved analytical methods for analyzing the failure surfaces of wood bonds.

Problem 2 – We have developed hydroxymethylated resorcinol as a primer for bonding wood surfaces to improve exterior durability. This primer improves wood bonds where wood either has been chemically treated (for biological protection) or is to be bonded to plastic materials. Its potential use in glassfiber-reinforced glulam beams in bridges and other engineered structures has been demonstrated. Recently a form of the materials more useful for industrial manufacturing has been developed. Work continues to develop the process by which it can be applied and used most effectively.

Problem 3 – For commercial viability, wood adhesives need to give improved performance to the bonded assembly or need to lower the cost of production. Using what we have learned about bond failures, we have made some improved epoxy adhesives. By learning how to more efficiently crosslink proteins, we have developed (with an outside company under a Cooperative Research and Development Agreement) adhesives that are much lower in cost while giving performance equal to that of commercial phenol-formaldehyde adhesives for bonding the face layers of OSB.

Problem 4 – Volatile organic compounds are emitted from adhesively bonded wood composite panels. Consumer and regulatory agencies need information about the types, quantities, and persistence of VOCs emitted from wood products to develop mitigation strategies. Accurate, standardized techniques are needed to collect, identify, and quantify the emissions from wood, during both manufacture and use. Because, increasingly, all products are expected to be recyclable, information on the recyclability of bonded wood products and the environmental fate and impact of the adhesives in those products is important.