Aim of study: Although treated panels make up a large portion of the plywood market, treatment with some wood preservatives has been known to cause some problems such as bonding failures besides the environmental pollution related to the disposal of chemicals after treatment. Formaldehyde release from wood based panels is also another problem regarding the indoor air quality. In the present study, it was aimed to investigate the formaldehyde emission contents of plywood panels treated with fire retardant chemicals.

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In the present study, it was aimed to investigate the formaldehyde release of plywood panels manufactured from beech, poplar, alder and scots pine veneers treated with 5 % aqueous solutions of commonly used fi re retardants: zinc borate, boric acid, monoammonium phosphate and ammonium sulfate. Two types of urea formaldehyde (UF) resin with different free formaldehyde ratios (0.16 % and 0.20 %) in adhesive were used as adhesive. Formaldehyde release of plywood panels was determined according to fl ask method described in EN 717-3 standard. As a result of this study, it was found that formaldehyde release from panels produced by beech, poplar, alder and scots pine veneers treated with zinc borate and boric acid were higher than those of control panels, while lower formaldehyde release was obtained for panels treated with monoammonium phosphate and ammonium sulfate. This is valid for all four wood species. Treatment of monoammonium phosphate and ammonium sulfate caused considerable reduction in formaldehyde emission from manufactured plywood panels. In some usage areas, where high strength properties are not expected, plywood panels manufactured from veneers treated with monoammonium phosphate and ammonium sulfate may be used for reducing formaldehyde release.

This study investigated the effects of different fire retardant chemicals on surface and thermal properties of veneer sheets. Beech (Fagus orientalis), alder (Alnus glutinosa), poplar (Populus deltoides) and scots pine (Pinus sylvestris) were chosen as wood species and zinc borate, borax, monoammonium phosphate and ammonium sulfate were chosen as fire retardant chemicals. The samples were impregnated by using the immersion method. Some surface properties such as colour measurements and surface roughness of the veneer sheets were conducted according to CIE L*a*b* system. Some thermal properties such as thermal conductivity of the veneer sheets were conducted according to standard and weight loss after combustion was determined by thermogravimetric analysis. Conforming to the results from the study, it was found that fire retardant chemicals increased the thermal conductivity and surface roughness of veneer sheets. Also, thermogravimetric analysis experiments showed that all of the fire retardant chemicals decreased the loss in weights.

The processing of wood-based panels such as plywood, particleboard and fiberboard, which are widely used in the furniture industry, with CNC (Computer Numerical Control) milling machines has been increasing recently. Even though CNC milling machines have many advantages for furniture producers, it is difficult to set process parameters to obtain the desired surface quality of the material. Therefore, it is necessary to determine the most suitable of these parameters for the surface quality of each wood-based panel. This study aimed to determine the effects of processing parameters on the surface quality of plywood, particleboard and medium density fiberboard (MDF) panels processed in CNC milling machines. Furthermore, the average surface roughness values of these panels were compared after CNC processing. Three spindle rotational frequencies (10.000, 14.000 and 18.000 rpm), three feed rates (5, 7, and 9 m/min) and two cutting tool diameters (2 and 5 mm) were selected as CNC processing parameters. To determine the surface quality of wood-based panels, the surface roughness measurements were performed according to DIN 4768 standard and three surface roughness parameters (Ra, Rmax and Rz) were determined. According to the results of this study, it can be concluded that the surface roughness values of wood-based panels decreased with increasing spindle rotational frequency and feed rate, while they increased with increasing cutting tool diameter. Among the wood-based panels used in this study, the lowest average roughness values were obtained for plywood samples.

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This study aimed to predict the CNC cutting conditions for the best wood surface quality, energy, and time savings using artificial neural network (ANN) models. In the CNC process, walnut, and ash wood were used as materials, while three different cutting tool diameters (3 mm, 6 mm, and 8 mm), spindle speed (12000 rpm, 15000 rpm, and 18000 rpm), and feed rate (3 m/min, 6 m/min, and 9 m/min) were determined as cutting conditions. After the cutting processes were completed with the CNC machine, energy consumption and processing time were determined for all groups. Surface roughness and wettability tests were performed on the processed wood samples, and their surface qualities were determined. The experimentally obtained data were analysed in ANN, and the models with the best performance were obtained. By using these prediction models, optimum cutting conditions were determined. Using the findings of the study, the optimum cutting condition values can be determined for walnut and ash wood with the smoothest and best wettable surface. Furthermore, in CNC processes using such materials, minimum energy consumption and shorter processing time can be obtained with optimum cutting conditions.

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