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In the article, the effect of the surface on the strength of the corner joint on the window was analyzed. The corner joint on the window is made in the variant with double and triple dowel and slot using PVaC adhesive. Samples were made from pine tree (Pinus Nigra). For research purposes, a special holder was made for the samples to enable testing according to the EN514:2018 standard method. The aim of the work is to determine the influence of the connection element on the strength of the corner joint of the window when using PVaC glue. The samples were divided into 2 groups of 30 samples each, depending on the number of dowels. The standard methods of statistical analysis were used. The test showed that the connection with triple dowel and slot has higher breaking strength values compared to double dowel and slot.

Limited information is available on end gluing hardwoods in contrast to softwoods, which have been extensively investigated. The objective of this study was to examine the influence of bending patern on bending strength of finger jointed beech wood. In structural uses finger jointing is finally the major method to end joint timber for the production of glue-laminated elements. There are no bending strength experimental results for finger-jointed hardwoods for investigations conducted in Serbia. Two finger jointed profiles were studied in accordance with DIN68140. The finger joints were made by side and by face of beam. Length jointed samples were loaded at the side and in the face. The obtained results led to the conclusion that the direction of load, gluing surface and the position of joint influence on the strength of continued longitudinal beams.

This paper investigates the impact of the top coating on the basic mechanical properties of a lacquered surface, including indentation hardness, scratch resistance and abrasion resistance. Three types of the top coating were used, including a 2K polyurethane coating, a 2K acrylate-isocyanate coating and a 2K alkyd-urethane coating. Samples of two wood species, spruce (Picea abies Karst.) and oak (Quercus robur L.), were used in this study, in order to determine whether the wood species, which is not in direct contact with the top coating, has an impact on the mechanical properties of a lacquered surface. The samples coated with a 2K acrylate-isocyanate coating showed the highest values of indentation hardness, in the samples of both wood species (1.34 N for spruce; 1.4 N for oak). The samples coated with a 2K alkyd-urethane coating showed the highest values of scratch resistance (20 N for both wood species) and abrasion resistance (mass loss of 480 mg after 700 cycles for both wood species). The results have shown that the wood species does not affect the value of indentation hardness, scratch resistance and abrasion resistance of a lacquered surface.

This paper presents the research of influence of wood surface preparation on the wetting ability of polyurethane coatings, by the method of contact angle. The samples were made of two species of Paulownia (Paulownia elongata and Paulownia fortunei). All the samples were processed by planing (molding). After molding, the samples were arranged in groups and sanded. In relation with wood grain direction, each group had a particular system of sanding, based on the numbering of sanding paper, program of displacement of sanding papers with different numbering and the direction of sanding. The quality of wood surface after sanding was expressed by the values of roughness parameters in the system 'M': Ra, Rz, Rv, Rp and Rt. The contact angle was measured using transparent polyurethane (PU) coating and distilled water. The influence of the system of sanding on the values of contact angle was analyzed by roughness parameter Ra.

This paper presents the research of influence of sanding, staining and the use of polyurethane and acrylic coating on the adhesion, scratch resistance and abrasion resistance of the coating. Objective was to determine the most important mechanical properties of lacquered surfaces, considering the application of Paulownia elongata and Paulownia fortunei, by using different systems of surface finishing. Cross cut method was used for measurement of adhesion. More accurate view of coating adhesion was obtained by measuring the scratch resistance. Abrasion resistance was tested by the method of free falling of abrasive particles. The applied system of sanding had no effect on the examined mechanical properties. Stained samples lacquered with PU coating showed better adhesion to the non-stained samples. Impact of staining on scratch resistance is not established. Stained samples showed greater resistance to abrasion for both wood species. Samples lacquered with PU coating showed the higher values of mechanical properties compared with samples lacquered with UV acrylic coating. Application of PU coating for surface finishing of Paulownia elongata and Paulownia fortunei is more adequate than the application of UV acrylic coatings, from the point of scratch resistance and abrasion resistance.

Products quality presents one of the main causes of every contemporary organized production, which includes it, in group of basic exit characteristics. According to national standard, quality mark is based on testing of its quality characteristics. A characteristic of quality has been divided into four groups of demands: functionality (functional dimensions and stability tests), rigidity, surface rigidity, quality of materials and work piece accuracy. Dining chair has been investigated by use of different wood joints, and some remarks on construction has been given. Two groups of investigated chairs has been mounted by use of metal fittings, and one group has been connected with wood dowels by use of PVA wood glue.