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Investigations on the Characterization of Various Adhesive Joints by Means of Nanoindentation and Computer Tomography
The mechanical properties of cured wood adhesive films were tested in a dry state by means of nanoindentation. These studies have found that the application of adhesives have an effect on the accuracy of the hardness and elastic modulus determination. The highest values of hardness among the tested adhesives at 20 °C have condensation resins: MF (0.64 GPa) and RPF (0.52 GPa). Then the decreasing EPI (0.43 GPa), PUR (0.23 GPa) and PVAc (0.14 GPa) adhesives. The values of the elastic modulus look a little bit different. The highest values among the tested adhesives at 20 °C have EPI (11.97 GPa), followed by MF (10.54 GPa), RPF (7.98 GPa), PVAc (4.71 GPa) and PUR (3.37 GPa). X-ray micro-computed tomography was used to evaluate the adhesive joint by the determination of the voids. It has been proven that this value depends on the type of adhesive, glue quantity and reactivity. The highest values of the void ratio achieve the PUR (17.26%) adhesives, then PVAc (13.97%), RRF (6.88%), MF (1.78%) and EPI (0.03%). The ratio of the gaps increases with the higher joint thickness. A too high proportion of voids may weaken the adhesive joint.
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.
Project entitled "an innovative product made of shrub willow for the wood industry" financed by Me&S under the "science for society" program
Influence of Chrysoporthe deuterocubensis Canker Disease on the Chemical Properties and Durability of Eucalyptus urograndis against Wood Rotting Fungi and Termite Infestation
In this study, the effects of stem canker disease caused by Chrysoporthe deuterocubensis on the chemical properties and durability of a Eucalyptus hybrid (E. urophylla x E. grandis) were investigated. Eleven-year-old healthy and infected trees were collected. The samples were grouped into four different classes based on the infection severity: healthy (class 1), moderately infected (class 2), severely infected (class 3), and very severely infected (class 4). The changes in chemical properties were evaluated via chemical analysis and Fourier transform infrared spectroscopy (FTIR) analysis. A resistance test against fungal decay (Pcynoporus sanguineus and Caniophora puteana) and termite (Coptotermes curvignathus) was also performed. The results showed that reductions in cellulose and hemicellulose content from 53.2% to 45.4% and 14.1% to 13.9%, respectively, were observed in the infected samples. Meanwhile, the percentages of lignin and extractives increased from 18.1% to 20.5% and 14.6% to 20.2%, respectively. The resistance against fungi and termites varied between severity classes. Generally, infected wood behaved better than healthy wood in terms of durability against fungi and termites. The durability classes for both tests were significantly improved, from resistant to highly resistant and poor to moderately resistant, respectively. These results suggest that E. urograndis that is infected by C. deuterocubensis might have a better potential use in lumber production with regard to its durability and processing cost compared to pulp and paper products.
Investigations into the Influence of Temperature on the Tensile Shear Strength of Various Adhesives
The temperature resistance of glued timber, which is crucial for glued wood construction, represents a significant assessment criterion. To gain insights into this aspect, this study utilized methods such as a shear strength test in accordance with EN 302-1:2013-06 under thermal loading (from 20 °C to 200 °C), and Differential Scanning Calorimetry (DSC) to determine the glass transition temperature (Tg). An increase in thermal load resulted in a decrease in shear strength and an increase in wood breakage. A hierarchy of adhesive groups was established based on strength performance and wood failure percentage (WFP) at 200 °C. Thermoset adhesives (MF: Melamine Formaldehyde, PRF: Phenol Resorcinol Formaldehyde) led the ranking, followed by elastomer adhesives (1C-PUR: One-Component Polyurethane, EPI: Emulsion Polymer Isocyanate), with thermoplastic adhesive (PVAc: Polyvinyl Acetate) last. Thermoset adhesives further cured under heat. PUR adhesives exhibited higher strength performance at 150 °C and lower temperatures.
The Impact of Sanding and Thermal Compression of Wood, Varnish Type and Artificial Aging in Indoor Conditions on the Varnished Surface Color
Adhesion promoters for gluing-selected materials in furniture industry
Surface treatment with plasma, corona, or air and the use of adhesion promoters (primers) are methods that can be used to improve the gluability of various materials. Adhesion promoters based on organosilicone compounds from the solventborne and waterborne catalyzed by isocyanates were used in the study. Dispersions and hot melt adhesives based on various thermoplastic polymers were used. Rheological properties and surface-free energy as well as dispersion and polar shares in substrate-adhesion promoter systems were evaluated. The strength and resistance of glue lines were determined. The tested primers and adhesives were classified as rheostable liquids, diluted in shear, not showing the flow limit. Covering of the surfaces of PVC foils and ABS, PS, PVC edges with primers caused increase in surface-free energy, especially polar share. Significant improvement of strength and resistance of glue-lines was observed (100% delamination in the substrate).
Gloss level, type of paper and colour of HDF boards finished with the energy-saving acrylic paint system
The global drive to eliminate mercury is stimulating the development of LED lamps for UV curing of coatings. Despite its many advantages, the transition to this system in the furniture industry presents technological issues. This paper aimed to determine the impact of the paint line’s individual technological and process parameters on the coating’s optical properties, such as colour and gloss of furniture components made of white-coloured light-weight boards. Samples were prepared under the conditions of an industrial paint line using LED and traditional mercury lamps at the rate of 50 m/min. The colour was tested using the CIELAB system on a BYK GARDNER spectrophotometer, while the gloss was measured using the PICO GLOSS meter. Based on the data obtained, the optical parameters were found to be highly stable irrespective of the power drop in the LED lamps. The coordinates L*, b* and gloss G were affected by the amount of topcoat and basecoat, the number of coats, the mercury lamps’ power and the panel grinding programs used. The results of the tests showed that high L* and b* values could be achieved by increasing the number of overlays. This solution also ensures less basecoat and topcoat consumption, contributing to large material savings.
Adhesive Bonding of Scots Pine Wood from the Szczecinek Forest District for the Production of Garden Equipment: An Experimental Investigation
This work aimed to determine the gluability of pressure-impregnated pine wood with two protection agents used in production technologies for garden equipment and their effect on the strength, water resistance and thermal resistance of joints, as well as their susceptibility to aging. The tests were carried out on Scots pine wood (Pinus sylvestris L.) purchased from the forest districts of the Regional Directorate of State Forests in Szczecinek town, Poland. For the impregnation, two commercial protection agents were used. The pressure impregnation of the elements and gluing with the PUR adhesive were carried out by a garden furniture manufacturer. The strength and durability after aging tests of glued joints were performed in accordance with the procedure described in Technical Approval No. AT-15-2948/00 and the PN-EN ISO 9142 standard. The collected experimental data can be used in technological solutions, mainly for processes which involve gluing wood after impregnation.
Impact of surface finishing technology on slip resistance of oak lacquer wood floorboards with distinct gloss levels
Correction: Physical and mechanical properties of wood treated with chitosan-caffeine formulations
Gloss of Varnished MDF Panels Veneered with Sanded and Thermally Compressed Veneer
The objective of this study was to investigate the gloss of different types of commercially manufactured varnish systems, including water-based (WB), polyurethane (PUR) and UV-cured (UV), applied on veneered MDF panels with sanded and thermally densified alder and birch wood veneers. The varnishes were applied at various numbers of layers on veneered panels. The gloss was measured at three angles of incident light: 20°, 60° and 85°. Statistical analysis showed that the type of varnish, the number of layers, the pre-treatment process, the wood species and direction of wood fibers significantly affect gloss of the coatings of veneered MDF panels. The type of varnish had a dominant effect on gloss. The highest gloss values were measured for the UV-varnished surface, and the lowest for WB- and PUR-varnished surfaces. Gloss was enhanced with an increase in the number of layers. Birch veneer provided higher gloss values compared to alder veneer. The gloss values measured along the wood fibers were higher than those measured across the fibers. No significant differences were found between the coatings created on sanded and thermally densified veneers for the average gloss values measured along the fibers at angles 60° and 85°. This study could have practical applications for producing value-added furniture elements using low-value wood species pre-treated by thermal compression.
