Evaluation of the Surface Irregularities of the Cross-Section of the Wood after CO2 Laser Cutting

The present paper deals with the analysis of cross-section surface irregularities after CO2 laser cutting. The surface irregularities of beech (Fagus sylvatica L.), oak (Quercus petraea), and spruce (Picea abies L.) wood were quantified by primary profile parameters using a digital microscope. The arithmetic mean height (Pa), used as the basic parameter, was supplemented by amplitude parameters (Pv, Pp, Pz) and the Psm parameter, through which the shape of the irregularity was specified in more detail. A statistically significant change was demonstrated when changing the values of the feed speed and the power of the CO2 laser. The results of this article confirm that the surface irregularities increased with an increasing laser power and decreasing feed rate. The scanned topographic images also provide a more detailed explanation of the measured P-parameters and point out the risks associated with the evaluation of the cross-section with the primary profile.

Influence of Flame Retardant Impregnation on Acoustic and Thermophysical Properties of Recycled Technical Textiles with the Potential for Use in Wooden Buildings

This article presents the results of an investigation of acoustic and thermophysical properties of insulation panels made from recycled technical textiles originating from the automotive industry. Measurements were performed on the samples of insulation panels (Senizol AT XX2 TL60), which were modified with liquid flame retardants (ISONEM^® ANTI-FIRE SOLUTION, ECOGARD^® B45, HR Prof). Another method of treatment was carried out by surface application of non-flammable facing (woven carbon fibre, nonwoven carbon fibre). Retardants were applied to the samples by surface spraying and soaking. The results showed a high ability of material to absorb sound in the frequency range 350 Hz–2 kHz. The sound absorption coefficient ranged from 0.82 to 0.9 in the frequency range 500 Hz–2 kHz. The noise reduction coefficient is 0.75. After material modification with the flame retardants, there was no significant change of sound absorption. The thermal conductivity coefficient of material before modification was 0.038 W⋅m⁻¹⋅K⁻¹. After application of the flame retardants, the thermal conductivity coefficient increased depending on type and method of retardant application in the range of 2.6–105.3%. The smallest change was detected after modification of material with ECOGARD^® B45.

Occupational Exposure to Dust Produced when Milling Thermally Modified Wood

During production, thermally modified wood is processed using the same machining operations as unmodified wood. Machining wood is always accompanied with the creation of dust particles. The smaller they become, the more hazardous they are. Employees are exposed to a greater health hazard when machining thermally modified wood because a considerable amount of fine dust is produced under the same processing conditions than in the case of unmodified wood. The International Agency for Research on Cancer (IARC) states that wood dust causes cancer of the nasal cavity and paranasal sinuses and of the nasopharynx. Wood dust is also associated with toxic effects, irritation of the eyes, nose and throat, dermatitis, and respiratory system effects which include decreased lung capacity, chronic obstructive pulmonary disease, asthma and allergic reactions. In our research, granular composition of particles resulting from the process of longitudinal milling of heat-treated oak and spruce wood under variable conditions (i.e., the temperature of modification of 160, 180, 200 and 220 °C and feed rate of 6, 10 and 15 m.min^-1) are presented in the paper. Sieve analysis was used to determine the granular composition of particles. An increase in fine particle fraction when the temperature of modification rises was confirmed by the research. This can be due to the lower strength of thermally modified wood. Moreover, a different effect of the temperature modification on granularity due to the tree species was observed. In the case of oak wood, changes occurred at a temperature of 160 °C and in the case of spruce wood, changes occurred at the temperatures of 200 and 220 °C. At the temperatures of modification of 200 and 220 °C, the dust fraction (i.e., that occurred in the mesh sieves, particles with the size ≤ 0.08 mm) ranged from 2.99% (oak wood, feed rate of 10 m.min^-1) to 8.07% (spruce wood, feed rate of 6 m.min^-1). Such particles might have a harmful effect on employee health in wood-processing facilities.

Functionality of Beech Bark in Adhesive Mixtures Used in Plywood and Its Effect on the Stability Associated with Material Systems

The results of research into utilizing grinded beech bark in order to substitute commonly used fillers in urea formaldehyde (UF) adhesive mixtures to bond plywood are presented in the present study. Four test groups of plywood with various adhesive mixtures were manufactured under laboratory conditions and used for experimentation. Plywood made using the same technology, with the common filler (technical flour), was used as a reference material. Three different concentrations of grinded beech bark were used. The thermal conductivity of the fillers used, viscosity and its time dependence, homogeneity and the dispersion performance of fillers were evaluated in the analysis of adhesive mixture. The time necessary for heating up the material during the pressing process was a further tested parameter. The produced plywood was analyzed in terms of its modulus of elasticity, bending strength, perpendicular tensile strength and free formaldehyde emissions. Following the research results, beech bark can be characterized as an ecologically friendly alternative to technical flour, shortening the time of pressing by up to 27%. At the same time, in terms of the statistics, the mechanical properties and stability of the material changed insignificantly, and the formaldehyde emissions reduced significantly, by up to 74%. The utilization of bark was in compliance with long-term sustainability, resulting in a decrease in the environmental impact of waste generated during the wood processing.