MOKUZAI HOZON (Wood Protection)

As a way to measure the solid content of fire-retardant in treated wood, we suggested to calculate it from the weight change of samples with water leaching. Thin samples of 5 wood species (Sugi, Akamatsu, Karamatsu, Douglas Fir and Western Hemlock) were treated with several concentration impregnant and water leaching test was conducted with these treated samples. It was indicated that the correction against elution from base material wood was needed for Karamatsu samples to derive the solid content of fire-retardant from weight change after the fire-retardant treatment or water leaching operation. The effects of leaching condition and drying temperature were examined, and appropriate leaching conditions were demonstrated. Additionally, we suggested the way to predict the solid content of fire-retardant from density of base wood.

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Low vacuum scanning electron microscope equipped with an energy dispersive X-ray detector (LVSEM-EDX) is capable of analyzing electrically non-conductive materials like wood without the need to render the surface conductive by applying a coating of gold, platinum or carbon. Hence, there is the possibility that LVSEM-EDX could be used to nondestructively follow the changes on the distribution of concentration of inorganic elements occurring at wood during water leaching procedures, because specimens can be observed initially (before leaching), and then repeatedly re-examined after leaching procedures. This study uses LVSEM-EDX to examine the time-dependent changes of the copper concentration distribution occurring at treated wood during water leaching procedures. Cryptomeria japonica (sugi) sapwood was treated by a copper azole wood preservative (CUAZ). We compared the concentration distribution of copper at treated wood surfaces before and after leaching. LVSEM-EDX revealed that copper concentration was higher in the surfaces of edges of the sample before leaching. Once the samples were leached out by water, the concentration of copper at wood surfaces increased and copper was more abundant in latewood. The concentration of copper gradually decreased when the samples were repeatedly leached out. We conclude that LVSEM-EDX is a valuable tool to follow the time-dependent changes on the concentration distribution of wood preservatives occurring at treated wood during leaching procedures.

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