Currently, emphasis is placed on using environmentally friendly materials both from a structural point of view and the application of protective means. For this reason, it is advisable to deal with the thermal modification of wood, which does not require the application of protective substances, to increase its service life. The main reason for the thermal modification of black locust is that although black locust grows abundantly in our country, it has no industrial use. It is mainly used outdoors, where thermal modification could increase its resistance. This article deals with the thermal modification of black locust wood (Robinia pseudoacacia L.) and the impact of this modification on the chemical components of the wood with an overlap in the change in mechanical properties compared to untreated wood. Static (LOP, MOR, and MOE) and dynamic (IBS) bending properties were evaluated as representative mechanical properties. At the same time, the impact of thermal modification on the representation of chemical components of wood (cellulose, lignin, hemicellulose) was also tested. As a result of the heat treatment, the mechanical properties gradually decreased as the temperature increased. The highest decrease in mechanical values found at 210 °C was 43.7% for LOP and 45.1% for MOR. Thermal modification caused a decrease in the content of wood polysaccharides (the decrease in hemicelluloses content was 33.2% and the drop in cellulose was about 29.9% in samples treated at 210 °C), but the relative amount of lignin in the wood subjected to increased temperature was higher due to autocondensation, and mainly because of polysaccharide loss. Based on the correlations between chemical and mechanical changes caused by thermal modification, it is possible to observe the effects of reducing the proportions of chemical components and changes in their characteristic properties (DP, TCI) on the reduction in mechanical properties. The results of this research serve to better understand the behavior of black locust wood during thermal modification, which can primarily be used to increase its application use.

Nowadays, the emphasis is on increasing the durability of all products. For this reason, it is also advisable to look into extending the durability of paper products. The main reason for using flax pulp is that flax and cotton pulp are widely used for the production of banknotes due to their higher strength. This paper deals with flax pulp with the addition of nanocellulose, which should further enhance the mechanical properties of the pulp. The tensile strength, breaking length, and tensile energy absorption index were evaluated as the key mechanical properties. At the same time, the effect of the addition of nanocellulose, whether it was added to the pulp mass or applied to the later produced paper as a spray or coating, was tested in comparison to paper without the addition of nanocellulose. The best mechanical properties, i.e., tensile strength, were achieved for the highest addition of 5% of nanocellulose into the pulp, at 24.3 Nm∙g⁻¹, and for the coating application, at 28.7 Nm∙g⁻¹, compared to the flax pulp without the addition, where the tensile strength was 20.5 Nm∙g⁻¹. The results of this research are used for the assessment of nanocellulose as a natural compatible additive to enhance the strength properties of cellulose-based materials.

Because there is a lack of wood resources in many countries, this work focused on pulp and paper production from the waste and agricultural residues of non-wood plants. The work aimed to pulp the nitrate-alkaline of black mustard (Brassica Nigra L.) and camelina (Camelina Sativa L.). The black mustard and the camelina were selected due to the expanding planted areas of these crops in the Czech Republic. To characterize the chemical composition of black mustard and camelina, cellulose, lignin, ash, and extractives were determined. Raw alpha-cellulose, beta-cellulose, and gamma-cellulose were also measured. The results showed that the content of lignin in non-wood plants is lower than that in softwoods. The cooked pulp was characterized by the delignification degree–Kappa number. Additionally, handsheet papers were made for selected samples of pulp. The handsheet papers were characterized by tensile index, breaking length, and smoothness and compared with commonly available papers.

Due to high levels of volatility in both the agricultural and the forestry commodity markets, specifically, of timber and agricultural crops, it is important to identify the risks associated with the stability of supplies necessary for the production of composite materials in the Czech Republic. This study aims to accurately estimate the availability of selected raw materials that contain lignocellulose over the next 20 years. In addition, their suitability for the production of composite materials is assessed based on their physical properties. Furthermore, in the event of scarcity involving timber in the European Union, recycled wood and post-harvest residues could replace conventional raw materials in wood-based composites such as particleboards and chipboards. The viable potential of Czech forests is predicted to be between 740 and 750 million cubic meters of timber. For agricultural crops, it is estimated at 0.9 million hectares of wheat and 0.5 million hectares of canola under the current EU biofuel policy and at 0.4 million hectares if this policy is removed. According to moisture and fibre analyses carried out in our study, the most suitable candidate for wood-based composites production is soft wood.

This work examines the effect of thermal modification temperature (180, 200, and 220 °C) in comparison with reference (untreated) samples on selected optical properties of six tropical wood species—Sp. cedar (Cedrala odorata), iroko (Chlorophora excelsa), merbau (Intsia spp.), meranti (Shorea spp.), padouk (Pterocarpus soyauxii), and teak (Tectona grandis). The main goal is to expand the existing knowledge in the field of wood thermal modification by understanding the related degradation mechanisms associated with the formation of chromophoric structures and, above all, to focus on the change in the content of extractive substances. For solid wood, the CIELAB color space parameters (L*, a*, b*, and ΔE*), yellowness (Y), ISO brightness, and UV-Vis diffuse reflectance spectra were obtained. Subsequently, these wood samples were extracted into three individual solvents (acetone, ethanol, and ethanol-toluene). The yields of the extracted compounds, their absorption spectra, and again L*, a*, b*, ΔE*, and Yi parameters were determined. With increasing temperatures, the samples lose brightness and darken, while their total color difference grows (except merbau). The highest yield of extractives (mainly phenolic compounds, glycosides, and dyes) from thermally modified samples was usually obtained using ethanol. New types of extractives (e.g., 2-furaldehyde, lactones, formic acid, some monomer derivatives of phenols, etc.) are already created around a temperature of 180 °C and may undergo condensation reactions at higher temperatures. For padouk, merbau, teak, and partially iroko modified at temperatures of 200 and 220 °C, there was a detected similarity in the intensities of their UV-Vis DR spectra at the wavelength regions corresponding to phenolic aldehydes, unsaturated ketones, quinones, stilbenes, and other conjugated carbonyl structures. Overall, a statistical assessment using PCA sorted the samples into five clusters. Cluster 3 consists of almost all samples modified at 200 and 220 °C, and in the other four, the reference and thermally modified samples at 180 °C were distributed. The yellowness of wood (Y) has a very high dependence (r = 0.972) on its brightness (L*) and the yellowness index of the extractives in acetone Yi(Ac), whose relationship was described by the equation Y = −0.0951 × Y(Ac) + 23.3485.

In this study, high-pressure laminates (HPL) impregnated with phenol-formaldehyde (PF) resins enriched with kraft lignin were developed. Pulverised kraft lignin was added to the commercial PF resin in the amounts of 1% and 5% (solid to solid). Laminates were manufactured using pressure impregnation of the resins into the papers and using hot pressing of HPL in a laboratory press. Laminates with a lignin content of 1% (L-LPF-1) showed the highest bending strength (72.42 MPa) and Brinell hardness (9.41); they also exhibited the best moisture uptake (9.61) and thickness swelling after immersion in water (3.32%). Except for impact bending, laminates with a lignin content of 5% (L-LPF-5) had worse properties. However, the differences between the variants are mostly not statistically significant and are comparable with the results of commercial PF resin. Scanning electron microscopy confirmed the homogenous structure of produced laminates and the occurrence of cohesive failures in ruptured L-LPF-1 laminates, whereas in ruptured L-LPF-5 laminates adhesive failures were also observed. Based on the conducted research it can be said that the utilisation of kraft lignin as an additive to PF resin (in the amount of 1%) has a positive effect on the produced HPL.