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)

The influence of short-term thermo-mechanical densification on the surface wettability of wood veneers

The study investigated the effects of short-term thermo-mechanical (STTM) densification temperature and pressure on changes in surface wettability of alder (Alnus glutinosa), beech (Fagus sylvatica), birch (Betula verrucosa) and pine (Pinus sylvestris) wood veneer. Veneer sheets were densified using pressure levels of 4 MPa, 8 MPa and 12 MPa at three temperatures: 100°C, 150°C and 200°C for a short time of 4 min. Wettability was determined by measuring contact angles with distilled water. The results were compared with those of non-densified veneers. The results showed that in arelatively short process time wettability can be changed significantly. The wettability analysis showed that STTM-densified veneer surfaces became more hydrophobic, which indicates poor wettability. However, it was found that even STTM densification of veneers provides stable properties; in particular, contact angle values were stable for 24 hours after densification, which is an important consideration for industrial applications. The effect of temperature on the contact angle was more evident than thatof pressure. Linear correlations were found between contact angle and both mass loss and compression ratio for all investigated wood species. These findings may be used to provide initial data for adhesive/ coating application processes in woodworking industry

Procjena dinamičkoga dodirnog kuta površine toplinski komprimiranoga bukova furnira

Rotary-cut veneer is characterised by two sides, namely loose and tight surface, which have different properties. The information concerning dynamic contact angle behaviour of veneer sides plays an important role in efficient use of veneer. Therefore, the objective of this study was to investigate the influence of different compression temperatures and pressures on various wetting behaviour of loose and tight sides of birch veneer. Veneer sheets were compressed in a hot press at temperatures of 150 and 180 °C using seven pressure levels from 0.5 to 3.5 MPa. Wettability of loose and tight sides of thermally compressed veneer was evaluated by measuring the dynamic contact angle with distilled water. The results showed that thermal compression decreased the surface wettability of both loose and tight sides of the samples, especially for veneer samples compressed at a temperature of 180 °C. Tight side of the samples had lower wettability than loose side, even after thermal compression. Therefore, adhesive or any kind of finishing can be applied to both sides of thermally compressed veneer sheets without having any adverse influence on not only the bonding quality but also the whole finishing process.Za ljuštene je furnire karakteristično da njihove dvije površine, tzv. otvorena i zatvorena strana, imaju različita svojstva. Za učinkovitu uporabu furnira važni su podatci o ponašanju dinamičkoga dodirnog kuta površina furnira. Stoga je cilj istraživanja bio ispitati utjecaj različitih temperatura i tlakova kompresije na ponašanje površina furnira pri kvašenju. Listovi furnira komprimirani su u vrućoj preši pri temperaturi 150 i 180 °C te uz primjenu sedam različitih tlakova, od 0,5 do 3,5 MPa. Ispitana je sposobnost kvašenja površine na obje strane toplinski komprimiranog furnira mjerenjem dinamičkoga dodirnog kuta primjenom destilirane vode. Rezultati su pokazali da toplinsko komprimiranje smanjuje površinsko kvašenje na obje strane furnira, posebice na uzorcima furnira koji su komprimirani pri temperaturi 180 °C. Zatvorena strana uzoraka furnira pokazala je manju sposobnost kvašenja nego otvorena, čak i nakon toplinske kompresije. Stoga se ljepilo ili neko drugo sredstvo za završnu obradu furnira može nanositi na obje strane toplinski komprimiranog furnira bez ikakve opasnosti od nepovoljnog utjecaja na kvalitetu lijepljenja i završnu obradu furnira

The influence of short-term thermo-mechanical densification on the surface wettability of wood veneers

The study investigated the effects of short-term thermo-mechanical (STTM) densification temperature and pressure on changes in surface wettability of alder (Alnus glutinosa), beech (Fagus sylvatica), birch (Betula verrucosa) and pine (Pinus sylvestris) wood veneer. Veneer sheets were densified using pressure levels of 4 MPa, 8 MPa and 12 MPa at three temperatures: 100°C, 150°C and 200°C for a short time of 4 min. Wettability was determined by measuring contact angles with distilled water. The results were compared with those of non-densified veneers. The results showed that in arelatively short process time wettability can be changed significantly. The wettability analysis showed that STTM-densified veneer surfaces became more hydrophobic, which indicates poor wettability. However, it was found that even STTM densification of veneers provides stable properties; in particular, contact angle values were stable for 24 hours after densification, which is an important consideration for industrial applications. The effect of temperature on the contact angle was more evident than thatof pressure. Linear correlations were found between contact angle and both mass loss and compression ratio for all investigated wood species. These findings may be used to provide initial data for adhesive/ coating application processes in woodworking industry

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

Mechanical Properties of Corner Joints Made of Honeycomb Panels with Double Arrow-Shaped Auxetic Cores

The development of both light and strong wood-derived materials is an interesting research area, particularly in terms of usability in, e.g., furniture constructions. Honeycomb panels being current industry standard are relatively thick (32 mm and 40 mm), thus their attractiveness in designing furniture is limited. In a few studies, it has been shown that honeycomb panels with paper cores are characterized by unsatisfactory mechanical properties, especially when the composite thickness is less than 20 mm. From the literature, it is also evident that mechanical properties might be improved by introducing auxetic features into the core structure. Even though it is a concept with great potential, there are a few studies dealing with honeycomb panels with auxetic cores made of paper. Furthermore, there is no research on the corner joints made from such material. For this reason, the aim of the study was to test the bending behavior of the corner adhesive joints made of honeycomb panels with double arrow-shaped auxetic cores. Within the research, the core cell was adopted based on literature and preliminary studies, paper auxetic cores were produced by the use of the designed and 3d printed device, and joints stiffness and strength were calculated analytically based on the experiment results. Evaluated corner joints stiffness, both in compression and tension test, is greater for samples made of panels with designed auxetic cores. Surprisingly, in the analyzed range of elasticity, it was statistically proved that the values of joint stiffness coefficient K did not vary significantly between compared joints pairs

Shear and adhesion strength of open and closed system heat-treated wood samples

This paper investigated the effects of heat treatment in open (atmospheric pressure) and a closed (under pressure) system on the shear and adhesion strength of Scots pine (Pinus sylvestris) wood. In addition, pull-off adherence testing was carried out of the coatings with water-based, polyurethane-based and oil/wax-based varnishes. Shear strength decreased significantly after heat treatment in Scots pine (31 % to 39 %) in open system, while it decreased between 2 % and 38% in the closed system without glue. The shear strength of the wood samples glued with glue was higher than the samples without glue at laboratory scale. The lower shear strength of modified wood could be attributed to other factors, such as the reduced chemical bonding or mechanical interlocking of adhesives, and the reduced strength of brittle modified wood substrate. With increasing heat treatment temperature adherence decreased. Maximum pull-off adhesion (4,80 MPa) was observed in the control samples coated with PU

Gloss Level of HDF Finished with Different Numbers of Layers and Hardened with UV Hg-Ga Lamps of Selected Power

A key feature of varnish coatings on furniture surfaces is their optical properties, which often determine customers’ purchase choices. Furniture may be produced using various boards, which are much cheaper than wood-based materials. For their finishing, among others, UV-cured varnish products are used. The aim of this study was to determine the effect of different types of HDF boards, the amount of basecoat and topcoat applied, the number of layers, and the different lamp powers used for hardening on the gloss of coatings obtained using UV technology. The gloss was tested with a photoelectric apparatus. An auxiliary parameter in the assessment of the gloss of the coatings was the surface roughness, which was measured with the Mitutoyo SJ-210 Analysis of variance (ANOVA) was used to obtain the results. Statistical considerations showed that the amount of topcoat applied, the power of the lamps, and the interactions between them had the greatest impact on gloss, followed by the number of layers. In general, the gloss of the coating decreased with a decrease in lamp power in the range of 120–60 W/cm and with an increase in the amount of topcoat applied

Mechanical and Chemical Resistance of UV Coating Systems Prepared under Industrial Conditions

In the upcoming years, it is expected that more furniture will be built from honeycomb panels due to the growing demand for lightweight, long-lasting furnishings. High-density fiberboard (HDF), previously used in the furniture industry as back walls in box furniture or drawer components, has become a popular facing material used in the production of honeycomb core panels. Varnishing the facing sheets of lightweight honeycomb core boards with the use of analog printing technology and UV lamps is a challenge for the industry. The aim of this study was to determine the effect of selected varnishing parameters on coating resistance by experimentally testing 48 coating variants. It was found that the interactions between the following variables were crucial in achieving adequate resistance: lamp power, the amounts of varnish applied, and the number of layers. The highest scratch, impact, and abrasion resistance values were observed for samples with optimal curing provided by more layers and maximum curing with 90 W/cm lamps. Based on the pareto chart, a model was generated that predicted the optimal settings for the highest scratch resistance. Resistance to cold liquids made with a colorimeter increases with lamp power