Enhancing durability of wood-based composites with nanotechnology

Wood protection systems are needed for engineered composite products that are susceptible to moisture and biodeterioration. Protection systems using nano-materials are being developed to enhance the durability of wood-based composites through improved resistance to biodeterioration, reduced environmental impact from chemical leaching, and improved resistance to ultraviolet (UV) degradation. Three approaches will be presented: (1) direct application of nanometals to wood-based products, (2) slow release of biocides embedded in nano-polymer matrices, and (3) controlled delivery of biocides with a nano-carrier. In the first approach, wood was vacuum impregnated with nano-sized particles of metals commonly used in wood preservative formulations (e.g., zinc and copper). Nano-zinc oxide particles were shown to be leach resistant, protected against UV degradation, and acted as a termite toxicant when compared to soluble zinc, a key component of the wood preservative ammoniacal copper zinc arsenate and zinc borate. In the second approach, self-assembling hyperbranched nano-polymers were loaded with an organic biocide. The complex surface of the nano-polymer encapsulated the biocide until a change in the physical environment (i.e., elevated heat or moisture) triggered its release. Nano-polymer encapsulation could provide long-term protection of composites as a surface treatment. In the third approach, nano-tubules made from an inert material served as a carrier for organic biocides. Loaded nano-tubules released the biocide in a slow, controlled fashion and provided superior protection of heat-labile organic biocides during the fabrication process compared to treatment with the biocide alone. Loaded nano-tubules may be used for surface application, pressure impregnation, or as an additive to engineered products.