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Investigation of Roughness and Adhesion Strength Properties of Pine and Poplar Wood Heat Treated in Air and under Vacuum after Artificial Aging
Heat treatment is an eco-friendly and efficient way to improve the defective properties of wood, such as its hygroscopic nature, the lack of dimensional stability, and low resistance against biological degradation, and to produce a green and sustainable wood material for construction and buildings. However, these treatments alter the substrates and could influence the performance of the coating products necessary to maintain the surface features in certain end-use sectors. In this study, the effects of heat treatment in air (HT) and under vacuum (VHT) on the surface properties of Scots pine (Pinus sylvestris L.) and poplar (Populus euramericana) wood were investigated. For this purpose, the samples were exposed to an artificial aging process. After the aging process, surface roughness and the adhesion strength behavior of the samples were measured. After the HT and VHT, poplar and pine wood samples showed different roughness. While the roughness value parallel to the fibers decreased in poplar wood, it increased in pine wood. The roughness value perpendicular to the fibers increased in both tree species. The maximum roughness value after UV aging was 62,622 in the VHT-200 group. Although with the UV ageing treatment, the adhesion strength was decreased in the samples heat treated in air, it was increased in the samples subjected to vacuum heat treatment. A lower loss of adhesion strength was observed in the heat-treated samples processed under vacuum compared to the heat-treated samples processed in air.
Adhesion of varnish coatings as a background for analogue and digital printing technologies
In analogue and digital printing technologies, from 3 up to 12 layers of lacquer products are applied. Technological parameters significantly influence the adhesion in the coating system. This article refers to the analysis of the influence of selected technological parameters, such as the number of layers, energy doses distributed by the radiators, and line speed, on the topography and adhesion of varnish coatings formed in the process of varnishing with rollers and UV-curing systems. The appropriately prepared surface can be used as a background layer for the analogue and digital printing technology. Manufacturers must adapt the production process to the particular varnish to obtain finished products with the best possible performance properties. The state of surface free energy and finally adhesion can be assessed by theoretically determining the possibility of an adhesive bonding between the product and the substrate, taking into account the assumptions of the adsorption theory of adhesion and measurement of the contact angle (Θ). An experimental confirmation of adhesion measurements included removing the coatings from the substrate via stamps glued to the coating.
Mechanical and Chemical Resistance of UV Coating Systems Prepared under Industrial Conditions Using LED Radiation
The furniture industry constantly strives to search for ecological and cost-effective solutions in the production of wood-based composites. It is anticipated that furniture with a honeycomb core and HDF-facing will gain market share. Understanding how specific technical and procedural factors on the finishing line affect the resistance of coatings on furniture elements made of honeycomb boards was the main goal of the study. With the use of a digital microscope, the roughness of two different types of HDF was tested. On the industrial UV LED+Hg finishing line, 198 different surface coating variations were produced by applying five or six layers of varnish applied, ranging from 3 to 30 g/m2 and hardening them with various surface power densities. On the basis of statistical tests, the influence of individual factors on abrasion, impact, and scratch resistance was determined. The nanointendence test of the coatings was used to measure the hardness and elasticity modulus. The coloring caused by coffee traces was checked using a colorimeter. The findings confirm the conception that LED+Hg lamp modules can replace mercury and gallium-doped mercury lamps.
Evaluation of Surface Roughness Parameters of HDF for Finishing under Industrial Conditions
One of the most important properties of the surface of wood-based panels is their roughness. This property determines the way of working with the material in the processes of gluing and surface varnishing. The aim of this study was to determine the effect of various sanding belt configurations and the feeding speed of the conveyor belt during grinding on the surface roughness of high-density fiberboards (HDF). The research material was prepared under industrial conditions. Three types of boards were selected for the tests. After grinding, the roughness parameters were measured both transversely and longitudinally relative to the grinding direction, using a Mitutoyo SJ-210 profilometer and the optical method. Based on ANOVA analysis of the data, it was found that the type of HDF boards used and the configuration of the abrasive belts had a statistically significant impact on the roughness. The samples for which the grinding process was performed with sanding belts of the highest grain size had the lowest roughness. For the amplitude roughness parameters, the direction of roughness measurement had a significant influence. These results may provide valuable guidance for the furniture industry in the preparation of HDF for furniture production.