At the frontiers of wood research, scientists are looking at “nano” qualities of wood pulp—even considering ways to use forest products to regrow ligaments and tendons in the human body. The pulp can also provide the basic ingredients for solar collectors and lightweight auto parts. But for the LBM industry, the most important new research into wood technologies centers on advances in adhesives for plywood and oriented strand board (OSB), as well as developments in cross-laminated timber, wood preservation, and energy efficiency.
Competition for Building Materials
Some of that research may generate an increase in the use of wood in areas far removed from building materials. One of the most visible areas of study is the U.S. Forest Service’s Cellulose Nano-Materials Pilot Plant at the Forest Products Laboratory (FPL) in Madison, Wis., which is producing two different nano-scale cellular materials.
The process for creating cellulose nanocrystals (CNC) has been around since about 1950. “When you remove part of the cellulose chain, the crystalinity increases,” says Alan Rudie, supervisory research chemist at the lab in Madison. “At the end of the process, what remains is almost totally crystalline. There is nothing in these crystals that can refract or absorb light.” In theory, it should be a colorless, clear solution. However, in practice, the solution is opaque and somewhat cloudy because of the way the crystals line up. According to Rudie, the crystals are estimated to be as strong as steel, at about one-fifth of the weight.
“Some of the groups we were working with were having trouble making the cellulose nanocrystals,” he says. “They realized that access to raw materials was the biggest impediment to research, so they asked the Forest Service to supply funding for a pilot plant to provide these materials.” This led to the FPL receiving $1.7 million to build the plant, which can now produce cellulose nanocrystals in amounts of 25 kilograms per batch at a rate of about 50 kilograms per week.
The other material is cellulose nanofibrils (CNF). These were discovered about five years ago and are produced from bleached wood pulp using an oxidation mediator called the TEMPO method. “We can produce the TEMPO-grade cellulose nanofibrils at about 4 kilograms per week,” Rudie says.
These technologies can also be blended with adhesives. “There has been limited experimentation here,” he says, “but it could potentially provide better gap-filling capability than an unsupported adhesive.”
According to Rudie, there are some possible applications of these technologies for building materials. “One group was looking at using the cellulose nanofibrils to reinforce wood structures. The cross-grain strength of wood is somewhat weak compared to the grain direction. We were interested in veneers, where the strength issue is a problem. We saw almost no strength improvement in the grain direction, but we did see a nice increase in the cross-grain direction.”
Where these technologies are of most interest are in areas other than building materials. One application is defense-related, including light-weight armaments. Another application relates to the coefficient of thermal expansion, with one group using organic conductors in an attempt to make solar collectors out of cellulose nanocrystal film.
“In the medical area, there is the potential to create synthetic ligaments and tendons out of these materials, since the cellulose is largely compatible with the human body,” he says. “The body then recruits cells that would fill in certain areas and potentially regrow the ligament or tendon.” A longer-term goal is to use the materials in polymers that could provide lighter-weight autobody parts for cars.
Advances in wood research and technology are creating new uses for wood outside of building materials. However, even more research is focused on improvements of wood in areas such as cross-laminated timber (CLT), adhesives, connection and assembly, wood protection, energy efficiency, and more.