Search Results (4)

To improve the estimation accuracy of wood density and study the linear correlation between drill feed resistance and wood density, a new micro drill instrument prototype that can simultaneously measure the rotation resistance and feed resistance of the drill needle was designed. The test tree species included hard and soft broad-leaved trees and coniferous trees, and the absolute dry density of each wood sample was measured. The drill resistance data were tested by our newly proposed prototype and a Resistograph 650-SC, and four linear models were established to define the relation between drill resistance and the absolute dry density of the wood. The results showed that (1) the statistical indicators of each model for our proposed prototype were better than the corresponding indicators of the Resistograph 650-SC for three of the four species tested; (2) the coefficient of determination of the linear regression model between the feed resistance of our proposed prototype and the absolute dry density of wood was 0.946; and (3) the statistical indicators of the model that included rotation resistance and feed resistance were better than those of the model that only including rotation resistance. Although the proposed prototype produced a competitive level of accuracy and explicitly demonstrated that including feed resistance improved wood density measurement accuracy, the prototype should be considered a first iteration as further hardware design changes and in-forest performance assessments across wider diverse set of test species are required before a conclusive evaluation can be rendered. Full article

Self-made shellac microcapsules and discoloration microcapsules in different proportions were added to water-based coatings and the influence of different proportions of self-healing discoloration microcapsules on the coating performance for Ebiara solid boards was discussed. Through a three-factor, two-level orthogonal experiment, the effects of the content of the addition of discoloration microcapsules, shellac microcapsules, and microcapsules on the performance of the coating were explored; the most influential factor of microcapsules was the shellac microcapsule content. Through the coating repair experiment, after 5 days of repair, the coating without adding shellac microcapsules does not display the repair effect. When the shellac microcapsules and discoloration microcapsules were added simultaneously, the width of the coating decreased by 3–6 μm after 5 days of repair, displaying a good repair effect. The shellac microcapsules have a great influence on the surface roughness of coatings. After adding the shellac and discoloration microcapsules, the hardness of the coating was not significantly affected. It was found that there was no chemical reaction between the coating and microcapsules. The best comprehensive performance was obtained by adding 15.0% shellac microcapsules in primer and 20.0% discoloration microcapsules in topcoat. The results provided a reference for multifunctional wood coatings. Full article

The structure of forests has changed with an increase in soft-wooded broadleaved species over the past decade. The demand for hard-wooded broadleaved species can be met by replacing them with compressed wood of soft-wooded broadleaved species. Existing compressed wood technologies do not fully take into account the density variations that exist along the height of a tree trunk. In this study, we examined the variability of birch and aspen microstructures along the height of the trunk, including vessels per square millimeter and the diameter (tangential and radial) of the vessel lumina. The research was carried out on aspen and birch species growing in Central Russia. The vessels per square millimeter in both species increased from the base to the top of the trunk and their diameters decreased from the base to the top of the trunk. Birch demonstrated greater changes in these values than aspen. There was a strong relationship between the diameter of the vessel lumina and the trunk height. A decrease in the density of the stemwood from the base to the top of the trunk was caused by an increase in the vessels per square millimeter. These results affected the density of the stemwood and determined the degree of compression as well as the initial size of the blanks required to obtain material with uniform quality indicators, regardless of the source location of the raw materials in the tree trunk. Full article

In order to protect the wood surface and improve the properties of coatings, microcapsules with healable and discoloration functions are produced, and their healable function is obtained using shellac, which can be cured at room temperature, as the repairing agent. In this paper, self-made shellac microcapsules and color-changing microcapsules were added to varnish in different proportions to form the composite coating on a wood board, and the color difference of the coating was measured at different temperatures to study the influence of microcapsules on the degree of surface color on the substrate. The effect of microcapsules on the healable performance of coatings on a wood board was studied by scratching the surface of the coating with a utility knife and observing the process of repair. The optimal sample was selected from the orthogonal experiment for the independent experiment. The surface roughness, hardness, infrared spectrum, and scanning electron microscopy of the optimal sample were tested, and the content in the optimal sample was further investigated. The results show that color-changing microcapsules have a color-changing effect on surface coatings based on wood boards, and shellac microcapsules inhibit the color-changing effect of color-changing microcapsules. Composite microcapsules can repair the cracks on the surface coatings of wood boards. In cases where shellac microcapsules can self-repair the coating, the color-changing effect is best when the content of color-changing powder is 15.0%. Full article