| dc.description.abstract | Engineered wood products (EWPs), for example, particleboard and oriented strand board (OSB), are normally made from wood residuals or small particles of underutilized wood species for replacing solid sawn products as its cost effective, more uniform, and a more efficient method of using available timber resources. Although, denser and more uniform than conventional wood, particleboard is a cheaper and low strength composite material. In addition, lower stability of OSB is the main obstacle in the expansion into a larger segment of the market; even though other properties are comparable to plywood. Thermal modification is a relatively new technology attracting the attention of many industries for improving stability in an environmentally friendly way, and the use of thermally modified composite panels for structural purposes is of increasing interest. Therefore, this research was carried out focusing on the manufacturing of particleboard and thermally modified OSB.
The purpose of the first aspect of the research was to investigate if the physical and mechanical properties of particleboard can be improved by using different types of raw material (juvenile wood, mature wood whole tree, mature wood heartwood from tamarack {Larix laricina (Du Roi) K. Koch)). For the second aspect of this research, the effect of heat-treatment temperatures (160°C and 175°C) on selected physical and mechanical properties of thermally modified OSB was determined.
The properties evaluated for both parts were bending (MOR and MOE) and bonding strength (IB), thickness swelling (TS), water absorption (WA), linear expansion (LE), surface hardness (H), and face screw withdrawal strength (FS). Results conducted from the first study showed that the mature whole tree board outperformed the minimum standard values on most selected properties. Comparing the effects of raw material, it is found that the heartwood board produced better physical properties and bonding strength compared to others, which is probably due to the high content of extractives present in the heartwood.
Results gathered from the second study indicate that wood variation not only exists in solid wood products, but also in the composite products. Low temperature treatment (160°C) displayed a better dimensional stability than the control group without largely affecting mechanical properties in a negative way, such as FS and hardness. However, high temperature samples (175°C) negatively affected mechanical properties, however, display better water resistance than the control group. For structural end use purposes, parallel to the long direction of OSB should be confirmed as it is the strength direction.
The results of this study suggest utilization of under-utilized species for
particleboard manufacturing in the panel industry is possible, and the increased life span of exterior applications by using a low temperature ThermoWood treatment on OSB is a feasible process to allow new applications for OSB, including areas of higher moisture content where OSB currently cannot be utilized in these conditions. | |
