Study On High Temperature Heat Treatment On Ash Wood Flooring

Basing on some prior studies, high temperature heat treatment in this study was derived from Finnish Thermowood method, but there were some adjusting in its earlier drying stage, because much hardwood have a susceptibility to many kinds of checks. It is a proven method for changing some defects of wood by some prior works, which wood were treated in the superheated steam at atmosphere pressure in a special equipment that can sustain the high temperature and moist environment for long. By and large, the durability and dimensional stability of wood can be mainly improved by this method, because some physical changes and chemical reactions in the main components and structure of wood would be happen, especially the hemicellulose is decomposed at different extent depending on temperature in the treating process (See chapter one and two). In this study, the ash wood (Fraxinus mandshurica) blanks for solid wood flooring were heat treated in high temperature on commercial scale based on laboratory experiments. Meanwhile, there were some analyses on issues of industrialization for this method in this study. The main results were summarized as follows:The color change of ash wood before and after high temperature heat treatment were investigated by CIE (1976) L~*a~*b~* color space theory with WSC-S Color Difference Meter in chapter three and four. The results showed that the color of treated wood is affected by the processing temperature, moreover, the change in L~* component can be used for quantitative analysis on color change. The higher the temperature, the darker the appearance, and furthermore, the color of treated ash wood by different processing temperature were similar to some valuable wood, for example, some rosewood species, teak wood, etc.. On the whole, the color of treated wood can be well replicated from laboratory experiments to commercial scale production.In chapter five and six, the effects of high temperature heat treatment on commercial scale experiments on mechanical and physical properties of ash wood were investigated respectively. 1) Mechanical properties? ? There was no distinct difference between tangential and radial directions MOE of treated wood, which was the same to the reference result. This method had side effects on tangential direction MOR and partial compressive stress perpendicular to grain, but had hardly any effects on tangential direction MOE, compressive strength parallel to grain, surface hardness. If comparing the mechanical properties of treated wood with the reference in use condition, it was concluded that the above mechanical properties of treated wood were better than the reference except for tangential direction MOR. 2) Physical properties? ? From dry to moist condition, the densities and hygroscopicities of treated wood were all less than the reference, the dimensional stability were improved, and that, the difference of EMC and tangential and radial swelling rate between treated and reference ash wood increased with RH, which can be explained by BET theory and the formula derived from it.Finally, Chapter seven focus on some issues of industrialization for high temperature heat treatment. 1) The contact angle of pure water droplet at the treated ash wood surface increased significantly, which mean that this method had side effects on interfacial properties between wood surface and paint. The treated wood surface wettability can be elevated by means of suitable sanding, moreover, adding surfactant in paint may be alternatively way for improving the painting effect of treated wood in commercial scale production. 2) In ground heating condition, the change of MC of treated wood was tiny and therefore the dimensional stability would be better than the reference, so the treated wood can be used as ground heating flooring material. 3) The total plant and equipment investment of high temperature heat treatment for 0.14 million M~2 annual capacity was about 1.5 million RMB. All kinds of production costs were 16.54 RMB/M~2 in total, and consequently the price of final product would be increase by 40 RMB/M~2 or so, which means that the treated wood flooring from common wood have more predominance than untreated valuable wood flooring in price war.As mentioned above, it is hoped that high temperature heat treatment will have a bright future in wood industry in China.