The effect of the initial modification of beech and spruce wood using a solution of caffeine and of a commercial product FN-NANO® FN-1 containing a water dispersion of TiO2 nanoparticles for increasing the service life of a transparent oil and acrylate coatings during 6 weeks of artificial accelerated weathering was tested. Changes in colour, gloss, and the contact angle of water were monitored. Degradation of the coating film was also evaluated visually and microscopically. The resistance of the coatings to mould growth was also subsequently tested. Based on the results, it is possible to recommend the initial treatment of spruce and beech wood with a 2% caffeine solution or 15% solution of FN-NANO® dispersion to increase the overall life of a transparent acrylic coating in exterior applications. No positive effect of the applied treatments was observed with the oil coating. In addition, lower concentrations of FN-NANO® did not have a sufficient effect, and the synergistic effect of using FN-NANO® in a mixture with a 1% caffeine solution was also not confirmed.

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This study compares the quality of wood from two distinct sites in the Czech Republic-from former afforested agricultural land and forest land. We compared the properties of Norway spruce wood (Picea abies Karst.) and Scots pine wood (Pinus sylvestris L.), the most important domestic tree species, to Douglas fir (Pseudotsuga menziesii (Mirbel) Franco), a North American tree species and a potential substitute for the domestic spruce. Wood density, modulus of elasticity (MOE), modulus of rupture (MOR) and impact bending strength were the properties tested that were used for comparing tree species. Without taking into consideration the site, the highest density values from the tested tree species were obtained for Douglas fir (0.568 g·cm −3 ), followed by the pine (0.508 g·cm −3 ) and the spruce (0.463 g·cm −3 ). The Douglas fir also dominated in the remaining assessed properties, whilst the influence of site was not confirmed, with the exception of MOE and MOR, and only for the Douglas fir wood, wherein higher values were obtained for forest land. In terms assessed Douglas fir properties, it exceeds the domestic softwoods and represents a possible suitable replacement for them. The site only plays a role in terms of the Douglas fir, and only for certain properties.

With the gradual decline in the proportion of spruce as the most important tree species in the Czech Republic, the importance of pine will increase. The test material for this study was selected from two localities with important representation of pure Scots pine stands. Two stands, representing clear-cutting and shelterwood regeneration methods were selected from each locality. In the case of shelterwood method, tree samples from a lower layer were cut down and subsequently evaluated in terms of the impact of the regeneration method on the density of the wood, the density of earlywood and latewood, the proportion of latewood and the width of the annual rings. These qualitative parameters of the wood were compared before and after the release of the parent stand canopy. The clear-cutting regeneration method served as a reference. The values obtained before the release of the parent stand canopy are significantly different from values after its removal (share of latewood 47.7% and 48.1% before the release in contrast to 39.5% and 39.1% after the release for the locality 1 and the locality 2 respectively). The shelterwood regeneration method has not a significant impact on the overall investigated characteristics. Most significant was the impact of the regeneration method on the distribution of properties along the trunk radius, where the shelterwood method shows a uniform density distribution from the pith to the bark. From the view of industry, therefore, it is not important for the final processing which part of the trunk the wood comes from.

This study provides a solution for the utilization of two waste materials, namely the residues of soft polyurethane foam from the production of mattresses and winter wheat husks. Thermal insulation panels with a nominal density of 50–150 kg/m3, bonded one-component moisture curing polyurethane adhesive, were developed, and the effect of the ratio between recycled polyurethane foam and winter wheat husk on internal bond strength, compressive stress at 10% strain, water uptake, coefficient of thermal conductivity, and volumetric heat capacity was observed. The developed composite materials make use of the very good thermal insulation properties of the two input waste materials, and the coefficient of thermal conductivity of the resulting boards achieves excellent values, namely 0.0418–0.0574 W/(m.K). The developed boards can be used as thermal insulation in the structures of environmentally friendly buildings.

The Scots pine (Pinus sylvestris Linnaeus) is one of the most important commercial tree species in Central Europe, yet we know very little about the variability of its wood properties. The aim of this study is to primarily analyse the impact of different tree growth rates and site characteristics on the shrinkage of Scots pine wood. The investigated forest stands are located at two sites of the Czech Republic that are characteristic for Scots pine silviculture. At each site, sample trees were selected from two stands representing two variants of the silvicultural treatment, i.e. a clear-cutting and shelterwood system with long regeneration period. Wood shrinkage in radial and tangential directions and volumetric shrinkage were determined in accordance with Czech standards. Lower values of shrinkage were found out in forest stands regenerated by the shelterwood method. The wood in the central part of the trunk shows lower shrinkage values than in the basal part in both stands. The unambiguous effect of the horizontal position in the trunk stem was demonstrated in forest stands regenerated by the clear-cutting method, whilst stands regenerated by the shelterwood method showed a more even distribution of shrinkage along the trunk width. Furthermore, it was found that the shrinkage of the Scots pine has a medium dependence on wood density.

Composites made from annual plants, such as winter rapeseed, can be used as an alternative to wood-based composites because of their ecological character, low price, as well as physical and mechanical properties. The goal of this study was to prepare such boards and evaluate their properties. Unmodified material and chemically and hydrothermally modified rapeseed particles glued by powder polyester glue were used. The characteristics measured were the internal bonding, swelling and moisture uptake over time, and surface soundness. The results showed that modification of the raw material influenced the properties of the resulting composites. The highest swelling values were exhibited by the boards with particles that were alkaline-modified. Boards made from hydrothermally modified particles achieved the highest strengths compared with the commercially produced boards. The alkaline modification of the particles resulted in a stronger adhesive bond between the particle and adhesive. During the internal bonding test, the boards made from the alkaline-modified particles exhibited cohesive failures in the particles. Therefore, the modification of the particles increased the mechanical properties of the boards, but the physical properties deteriorated.

Material alternatives to wood, such as rape straw, are needed for the production of composite materials. This study performed an analysis of rape straw as a composite material source for production. There were three types of rape straw particle modification: untreated particles as reference variant, boiling in water, and soaking in sodium hydroxide (NaOH) solution. The pH and calorific value were highest for the variant soaked in NaOH. The total elemental content and the elements on the rape straw surface varied between variants. The modification method chosen influenced the pH, calorific value, elemental composition, and contact angle. Keywords INTRODUCTIONRecently there has been an effort to develop new composite materials using alternative sources of raw materials. This trend is largely explained by population growth, which contributes directly to a limited supply of natural resources, as well as wood shortage in all wood processing industries (Galor and Weil 2000;Bektas et al. 2005;Seintsch 2011;Lauri et al. 2012). One alternative source of raw materials is post-harvest rapeseed crop residue (Mohanty et al. 2002;Dziurka et al. 2015). As a prospective raw material, rapeseed has many advantages, as it is available in large quantities and is not yet used in other products with high added value (Bečka et al. 2007;Dukarska et al. 2017). However, waxy and siliceous substances are present on the surface of winter rape stems, which prevents the formation of quality adhesion between particle and adhesive (Grigoriou 2000). This is the main disadvantage of particles from annual plants compared to wood particles. The chemical composition differs between internal and external areas of the stem because of cuticles and epicuticular waxes (Wiśniewska et al. 2003;Trischler, and Sandberg 2014). The surface has a strong impact on the water contact angle, which deteriorates the wetting of particles by adhesives, since adhesives used in particleboard production are mainly water-based (Wiśniewska et al. 2003). Therefore, it is necessary to pre-treat these particles from annual plants before the production of the composite material itself (Mahlberg et al. 1999;Cao et al. 2017). This modification can PEER-REVIEWED ARTICLE bioresources.com Částková et al. (2018). "Modified rape straw," BioResources 13(1), 104-114. 105 be done in various ways (Pelaez-Samaniego et al. 2013;Trischler and Sandberg 2014). Boiling in water is regarded favorably as a treatment due to its ease of implementation (Bekhta et al. 2013). An alternative is alkaline treatment, which breaks ester linkages between wax and lignocellulose, as well as dissolving wax and lignin (Binod et al. 2010;Wan et al. 2011). In this study, winter rape chips were modified by applying hydrothermal and chemical (soaking in sodium hydroxide) processes (Xie et al. 2010;Bekhta et al. 2013). It is assumed that the modification destroys the waxy, siliceous substances on the surface of the chips and consequently improves adhesion in the composite product. This study characterized the phys...