Experimental Studies of the Physical and Mechanical Properties of Glued Building Materials Based on Modified Veneer

Today, glued timber products occupy a significant place in the volume of finished products of modern construction and woodworking enterprises. Plywood is one such product. The durability and structural characteristics of plywood depend on the quality of binder, the type of wood and the quality of veneer. The paper explores the technology of ultraviolet treatment of thermally modified birch veneer with subsequent production of waterproof plywood. The results of a study on the influence of the operating parameters of veneer modification on the complex of sorption and strength characteristics of plywood materials are presented. It is established that the combination of thermal modification of wood throughout the entire volume with surface treatment with ultraviolet radiation allows creating glued wood material with increased water resistance and high-quality adhesive interaction.

Effect of Different Hardwood Species and Lay-Up Schemes on the Mechanical Properties of Plywood

In Estonia, hardwoods form approximately 50% of all forest area, where the main species are birch (30%), gray alder (9%), aspen (6%) and black alder (4%). Birch has been extensively used by the veneer-based industry, but species like black alder, gray alder and aspen have not been commonly used by the veneer-based products industry due to the lower quality of this resource. The aim of this research is to determine the effect of different lay-up schemes and usages of gray alder, black alder and aspen on the mechanical properties of plywood, by replacing birch veneer in the plywood core with alternative wood species. The main veneer and plywood characteristics will be evaluated according to the current standards, e.g., veneer strength perpendicular to grain, plywood bonding and bending strength, and modulus of elasticity. All processing parameters will be kept similar to those used generally by birch plywood manufacturers. The results showed that birch and black alder plywood panels had generally the highest bending strength properties, followed by grey alder and aspen. It was also found that, for proper gluing, birch veneers had the lowest glue consumption, 152 g/m2, and aspen had the highest glue consumption, 179 g/m2. It was found that when lower density wood was used in the plywood, the product density increased. Low density wood veneers had higher glue consumption, and also higher compaction in thickness than birch veneers under the same pressure. Overall, it was shown that the wood species used in this study have slightly lower strength properties, but with proper lay-up schemes, these wood species could be successfully used by the veneer-based products industry.

The accuracy of holes drilled in the side surface of plywood

Dimensional accuracy of machining translates into susceptibility to defects in assembly of furniture elements. In the initial drilling phase, the tip of the drill may slip due to the properties of the workpiece, which may result in inaccurate machining. Taking this into account, it was decided to investigate this phenomenon for drilling in the side of the plywood board. Samples for testing were made of 18 mm thick, 13 layer birch-alder plywood, covered with melamine film, glued with phenol-formaldehyde glue. With the use of an industrial dowel drilling machine, 30 holes in each of three examined layer were made. All holes were made parallel to the layers – on the side of the plywood board, and their axes were located in three adjacent layers: the birch veneer layer, the adhesive layer, and the alder veneer layer. Two types of geometric accuracy of holes were analyzed: the distance between the real center of the hole and the nominal position and also the inclination of the hole axis from the nominal axis. The holes made in the adhesive layer showed approximately twice larger deviations compared with the holes made in two adjacent layers of veneer. There was no significant relationship between the deviations of the angle of holes axis and the inaccuracies in the position of their centers. Main conclusion: When drilling in the side surface of the plywood board, less accurate holes are obtained if the hole axis is located in the adhesive layer, and there is more accuracy if the hole axis is located in the veneer layer.

Modification of veneer by amidophosphate for the manufacture of fire-resistant plywood

Целью работы являлось модифицирование березового шпона амидофосфатом с тем, чтобы из него по общепринятой технологии можно было изготавливать огнезащищенную водостойкую фанеру. В основу метода исследования положен прием пропитки шпона антипиреном водным раствором амидофосфата в двух вариантах: капиллярная пропитка и диффузионная пропитка. При этом изучали влияние температуры пропитки и продолжительности при переменной концентрации пропиточного раствора. В результате работы установлено влияние параметров в виде линейных эффектов и эффектов взаимодействия на содержание абсолютносухого антипирена. Используя корреляционные зависимости и функцию желательности стало возможным при уровне обработки в интервале 14,5 23,5 сухого содержания антипирена получить фанеру, характеризующуюся отсутствием самостоятельного горения и тления при удалении источника зажигания с потерей массы 4,4 5,9. При этом прочность изготовленных образцов фанеры оказывается удовлетворительной, например, предел прочности при изгибе составляет 77 100 МПа для исследуемых вариантов, при требованиях отраслевых технических условий не менее 60 МПа. Полученные результаты предназначаются для разработки производственного регламента изготовления фанеры с областью применения, где имеются ограничения по горючести и водостойкости. В работе получены выводы по рецептуре огнезащитного состава в связи с условиями образования фанеры на фенолоформальдегидном клее и рекомендации по организации производства трудногорючей фанеры с дополнительными технологическими операциями и оборудованием узла пропитки шпона и его сушки после пропитки раствором антипирена с тем с максимальным приближением к действующему режиму изготовления стандартной фанеры. The aim of the work was to modify the birch veneer with amidophosphate so that fireproof waterresistant plywood could be produced from it according to the generally accepted technology. The method of study is based on the reception of impregnation of veneer with flame retardant aqueous solution amidophosphate in two versions capillary treatment and diffusion impregnation. The influence of impregnation temperature and duration at variable concentration of impregnating solution was studied. As a result of the work, the influence of parameters in the form of linear effects and interaction effects on the content of absolute dry flame retardant is established. Using correlation dependences and desirability function it became possible to obtain plywood characterized by the absence of selfcombustion and decay when removing the ignition source with a loss of weight of 4.4 5.9 at the level of treatment in the range of 14.5 23.5 of dry flame retardant content. In this case, the strength of the manufactured plywood samples is satisfactory, for example, the bending strength is 77 100 MPa for the studied variants, with the requirements of industry specifications of at least 60 MPa of at least 60 MPa. The results obtained are intended to develop industrialstrength regulation for manufacture of plywood for various applications where there are restrictions on Flammability and water resistance. This paper has presented insights on the formulation of a flame retardant in connection with the conditions of formation of a phenolformaldehyde plywood adhesive and recommendations on the organization of production of hard combustible plywood with additional technological operations and equipment of the node impregnation of veneer and drying after the impregnation with a solution of flame retardant with the maximum approximation to the current mode of production of standard plywood.

Novel Lightweight Semi-Finished Products Made of Poplar Veneer Plywood with Basalt Fibre Reinforcement

Veneer plywood is established in building construction, interior finishing and vehicle construction. Particularly in automotive or ship interior applications, the requirements with regard to strength and stiffness properties are increasing. At the same time, the weight of the panel materials used is to be reduced. The development presented here is a new type of lightweight basalt fibre-reinforced poplar veneer plywood and at the same time rigid alternative to the established birch veneer plywood. By adapting the adhesive and the reinforcing semi-finished products, the material and manufacturing costs are comparatively low. The bonding of the fibre reinforcement to the carrier material is achieved by means of adapted wood adhesives (e.g. polyvinyl acetates), which are also used as matrix material for the fibre reinforcement. An application of the reinforcement layer is integrated into the coating process (e.g. with High Pressure Laminate HPL decorative fabrics) of the carrier material. Essential advantages compared to conventional board materials are shown in this paper. The research results were achieved at the Institute for Structural Lightweight Construction of the TU Chemnitz in cooperation with the company Toms Gerber GmbH within the ZiM cooperation project FuBa.

THE IMPACT OF HARVESTER CALIBRATION ON THE ACCURACY OF BIRCH VENEER LOGS MEASUREMENTS BY MEASURING DIAMETER IN SHORT INTERVALS USING ELECTRONIC 3D SYSTEMS

Accurate calibration of the harvester head relies on accurate manual log measurements. According to the recommended calibration procedures as proposed by the harvester manufacturer the differences between the volume measurements from harvester measurement system and the caliper-and-tape system must be within ± 3% and harvester diameter measurements within ± 6mm of manual measurements in 80% cases. Requirements in Latvia stipulate that total volume measurement accuracy levels must be within ± 5% of actual volume if veneer or birch logs are being harvested, ± 3% if saw logs are being harvested and ± 10% if pulp wood or fire wood are being harvested. The purpose of this study is to assess the impact of harvester calibration on the accuracy of birch veneer logs measurements by Measuring Diameter in Short Intervals using electronic 3D systems when different double bark volume determination algorithm are used in harvester and stacionar measurement system. The research was carried out in December 2016 in the region Latgale in Latvia. The wood felling area was chosen - Mercurialiosa mel. For volume estimation the sequent measurement equipment were applied: harvester Ponsse ERGO 8W, harvester information system Opti 4G and electronic 3D scanner system Elmes 3600. The research is a continuation to the work done in the project „Harmonisation of piece-by-piece measurement methods of roundwood approved by Standard LVS 82:2003 „Apaļo kokmateriālu uzmērīšana” [6], the project “Harmonization of piece-by-piece measurement methods in all stages of roundwood manufacturing processes” [7] and the project "Investigation and evaluation of the methodology of determination of solid volume according to the stacked volume on roadside and in forwarder loads for logistics purposes in LATVIA" [8].

The Effect of Hydrothermal Treatment on the Color Stability and Chemical Properties of Birch Veneer Surfaces

The effects of hydrothermal pre-treatment on the color of silver birch veneer were determined. Spectrophotometric and chemical analyses of the veneer by means of extraction were conducted to determine the detailed chemical characteristics of the veneers. Results from spectrophotometric analysis revealed a significant increase in lightness (L*) and a decrease in yellowness (b*) in the veneer produced from a log soaked at 70 °C in short-term. Conversely, the effect of long-term storage resulted in a significant reduction in L* and an increase in b*. Chemical analyses of the veneer extract identified a moderate negative correlation between soluble proanthocyanidins content and treatment temperature. A higher amount of wood extractives, such as lipophilic extractives, free monosaccharides, and other organic substances, were obtained from wood material soaked at 70 °C than at 20 °C, which was most likely due to moderate chemical changes during treatment. Comparison of the results between dried veneers and wet veneers from the water extraction study revealed that the dried veneers had higher amounts of lipophilic matter and less water-soluble organic matter than the wet veneers. Other aspects of the loss of soluble proanthocyanidins in the birch veneer during plywood manufacturing are discussed.