Holistic approach to wood protection

Abstract

When untreated wood is exposed to adverse outdoor conditions, nature has a series of chemistries to degrade it to its original building blocks of carbon dioxide and water. Fungi, termites, heat, moisture, ultraviolet (UV) energy, and chemicals take their toll on the performance properties of wood. We tend to study each of these degradation chemistries as individual events but, in fact, they are all connected by five basic chemistries: hydrolysis, oxidation, dehydration, reduction, and free radical cleavage. If we look more broadly at the commonalities involved in these chemistries, we can take a more holistic approach to the protection of wood through chemical modification. For example, simple acetylation of wood results in a lowering of the equilibrium moisture content and increases dimensional stability. The mechanism is simple bulking of the cell wall to near its elastic limit and substituting a less hydrophilic group on the hydroxyl groups in the cell wall polymers. This same chemistry increases biological resistance. The resistance to biological attack is probably due to lowering the moisture content of the cell wall below that needed for biological activity and may be, in part, due to a change in conformation and configuration of the substrate. If the bonded chemical contained a halogen, for example, the reacted wood would not only have the improved properties listed above but would also increase resistance to thermal degradation. If the bonded chemical contained a free radical scavenger, resistance to UV radiation could be improved. All of these improvements in performance can be achieved using one chemical reaction system interfering with hydrolysis, oxidation, reduction, dehydration, and free radical chemistries.

Citation

Rowell, Roger M. 2006. Holistic approach to wood protection. Wood Protection, 2006 : March 21-23, 2006 ... New Orleans, Louisiana, USA. Madison, WI : Forest Products Society, 2006: pages 115-119.