Optically transparent wood is a type of composite material, combining wood as a renewable resource with the optical and mechanical properties of synthetic polymers. During this study, the effect of monochromatic UV-C (λ—250 nm) radiation on transparent wood was evaluated. Samples of basswood were treated using a lignin modification method, to preserve most of the lignin, and subsequently impregnated with refractive-index-matched types of acrylic polymers (methyl methacrylate, 2-hydroxyethyl methacrylate). Optical (transmittance, colour) and mechanical (shore D hardness) properties were measured to describe the degradation process over 35 days. The transmittance of the samples was significantly decreased during the first seven days (12% EMA, 15% MMA). The average lightness of both materials decreased by 10% (EMA) and 17% (MMA), and the colour shifted towards a red and yellow area of CIE L*a*b* space coordinates. The influence of UV-C radiation on the hardness of the samples was statistically insignificant (W+MMA 84.98 ± 2.05; W+EMA 84.89 ± 2.46), therefore the hardness mainly depends on the hardness of used acrylic polymer. The obtained results can be used to assess the effect of disinfection of transparent wood surfaces with UV-C radiation (e.g., due to inactivation of SARS-CoV-2 virus) on the change of its aesthetic and mechanical properties.

The use of additive technologies keeps growing. Increasingly, flammable powder materials are also used in additive technologies, and there is a risk of explosion or fire when using them. The current article deals with the determination of fire parameters of a powder sample of polyamide Sinterit PA12 Smoth in accordance with the EN 14034 and EN ISO/IEC 80079-20-2 standards. For that purpose, a sample at a median size of 27.5 µm and a humidity of 0% wt. was used. The measurements showed that the maximum explosion pressure of the PA12 polyamide sample was 6.78 bar and the value of the explosion constant Kst was 112.2 bar·m·s−1. It was not possible to determine the MIT value of the settled dust, since the melting point of polyamide sample is low. The MIT of the dispersed dust was 450 °C. Based on the measured results, it can be stated that the powdered polyamide PA12 poses a risk in terms of explosions and fires. Therefore, when using polyamide PA12 in additive technologies, it is necessary to ensure an effective explosion prevention.

This paper presents a study into dynamic behaviour of the methylene blue adsorption (MB) on activated carbon. Effect of four parameters were studied: effect of the adsorbent dosage, effect of contact time, effect of pH, and effect of the initial concentration of methylene blue. The adsorption kinetic data were modelled using the pseudo-first and pseudo-second orders. Results show that, based on the experimental data, the pseudo-second order could be considered satisfactory. Thermodynamic parameters proved that adsorption of dye was spontaneous owing to increase in temperature and endothermic nature. Taguchi method was applied to determine the optimum conditions for removal of methylene blue by activated carbon. The optimum conditions were found to be pH = 7, contact time 60 min, initial concentration of MB 4 mg/L.

The study was focused on describing ultraviolet-visible spectra of the humic substances, humic acids and fulvic acids isolated from four Slovak soils. The samples were heated in a laboratory furnace, to simulate soil behaviour during fires. The absorbances at the wavelengths corresponding to the selected chromophores and specific wavelength for groups of substances were compared. Analysis of the UV -VIS spectra of the extracted humic substances may indicate the directions of interest in the changes in soil organic matter, along with the changes in external conditions, such as natural fires.

The objective of this manuscript is to report experimental results concerning the effect of accelerated UV-C ageing on the properties of samples of halogen-free sheaths of power cables. Two samples of halogen free sheaths of power cables of Vuki a.s. CHKE-V E30 and Nexans 273-K3 HERP/CWB/2SZH were studied after exposition on the UV-C radiation in a closed chamber. Degradation was monitored by the change in infrared spectra of the samples, their hardness and colour. Based on the observed changes, it can be argued that exposure to the UVC radiation affects the observed properties on the surface of the studied samples. All the observed changes were due to the rupture of the bonds towing to the absorption of UV-C radiation.