Adhesives

With more and more interest in CLT as well as wood-based composites, the topic of adhesives must, of course, be “front and center.”

One organization doing work in this area is the Wood-Based Composites Center (WBCC) at Virginia Tech (Blacksburg, Va.), which is funded by the industry on a global basis and subsidized by the National Science Foundation. “Our research is focused exclusively on structural and non-structural wood-based composites,” says Chip Frazier, Ph.D., director of the WBCC, and professor of Sustainable Biomaterials at Virginia Tech. “We are involved in a lot of fundamental, pre-competitive research that is being requested by the industry.”

One project involves modeling adhesive penetration into wood substrate on a micron scale, then trying to predict the performance of the bond line. The research has implications for OSB and plywood, as well as for furniture manufacturers.

“Everyone believes that the adhesive penetration into wood is critical, but we can’t actually prove it,” says Dr. Frazier. “We are using three-dimensional models and developing a micro-mechanical model prediction of how the bond line should perform.”

WBCC also conducts research on blending efficiency and resin distribution in the manufacturing of OSB. “There is a rotating drum blender, where the adhesive is sprayed onto the OSB flakes,” Frazier says. This work is being conducted at the University of British Columbia. “They want to develop a mathematical model of the blender in order to better understand how it operates, and how that impacts adhesive distribution.”

“When you talk about products like OSB and particle board, it is amazing just how little adhesive is actually used,” he says. “Under the circumstances, the process is very sensitive to the quality and efficiency of distribution—getting the resin everywhere it needs to be and avoiding ‘clumping,’ which represents inefficiency of distribution. The goal is to be able to reduce the costs associated with this process.”

One company paying attention to adhesives research is Weyerhaeuser. “Something to look for in the future is the advancement of bio-based adhesives in the OSB and composite-engineered wood products category,” Bradshaw says. “I think it will soon get to the point where the bio-based adhesives will get down to a price point that allows them to be substitutions for the petroleum-derived adhesives currently being used.”

The Natural Resources Research Institute at the University of Minnesota (NRR) is studying mineral-bonded fiber composites (also called inorganic-bonded fiber composites). “There is a lot of research on bio-based resins as a way to compete with petrol-based resins,” Donahue says. “However, we are trying to change that paradigm. Instead of using resins, we are working on methods that involve taking wet strands or fibers, combining them with a mineral mix, pressing it into a board, and curing the board with no added heat. The upside is the ability to make a panel product using far less energy.”