In Quebec and around the world, wood is considered a fine, strong material, but one that requires regular and meticulous maintenance, a characteristic that makes it less desirable when marketed for exterior applications compared with composites and other alternative materials. It is therefore important to determine the surface behaviour of softwoods in order to understand the short- and medium-term problems related to their performance, including colour stability and the appearance of flaws resulting from the excudation of extractives in eastern species like black spruce and balsam fir. We believe we have sufficient expertise to tackle these problems and identify the cause of the colour degradation and adhesion problems: 1. review lumber sorting methods and understand the source of the problem; 2. identify the physical and chemical cause of surface problems after accelerated weathering; 3. develop wood surface treatment methods to set or eliminate extractives; and 4. add microparticles or nanoparticles to wood to reduce the absorption of UV rays.
Many of the obstacles to good performance of wood films are related to poor adhesion of the film to the surface of the wood. This is attributable in part to the fact that the film does not penetrate the wood surface. One prerequisite is that the liquid film wet the surface. Once the surfaces are machined (planning/sanding), wettability may decrease as a result of changes in the chemistry of the surface. With spruce and pine, this occurs in four to five days after machining, and the surface is less active and harder to wet. We need evidence that such changes can occur in wood in such little time, and this has implications in cases where high film durability is required. Because this is not always possible, there is a need to develop methods of reactivating the wood by removing harmful extractives from the wood surface. We plan to use plasma techniques to reactivate the surfaces and remove extractives with low molecular mass that prevent films from adhering. This flash treatment is expected to have the added benefit of sterilizing the surfaces and thus minimizing the potentially negative effect of micro-organisms on adhesion.