This paper deals with the effect of UV light through window glass on the changes in colour of surfaces of uncoated and clear-coated thermally modified wood, and on chemical changes of surfaces of uncoated thermally modified and unmodified wood. Discoloration of the uncoated wood samples and those treated with three commercial transparent coatings (two-component polyurethane varnish, water-borne varnish, and nano-impregnation) was measured spectrophotometrically using CIELAB parameters (L*, a*, b* and DE*). FTIR spectroscopy was used to study chemical changes caused by UV irradiation. Colour change (DE*) was recorded in all tested wood samples after exposure to UV light, and the smallest discoloration was recorded in wood samples coated with two-component polyurethane varnish. FTIR spectroscopy results show that thermal treatment and exposure to UV light modified the chemical structure of wood surface and that the thermally modified samples exposed to UV light showed similar changes as unmodified samples exposed to UV light, but less pronounced.
a Wood extractives, especially polyphenols, have great influence on the xylem colour of many wood species, which affects the success of hydrothermal wood processing, such as wood drying. One such wood species is European black alder (Alnus glutinosa (L.) Gaertn.), which is prone to forming intense and uneven reddish-orange or reddish-brown discolourations immediately upon harvesting and processing. However, there is lack of published scientific data on the wood and bark extractives of black alder, as well as the most suitable solvents to extract them. In this work, total soluble extractives, phenols, and flavonoids have been quantified in the wood and bark of black alder. Furthermore, the influence of four different polar organic solvents and deionized water on extractives removal yields has been measured. It was found that the bark has much higher levels of extractives as compared to the wood. Furthermore, it has been found that the highest extractive yields were obtained by using methanol as the extraction solvent for all observed compound group classifications.
Natural polymeric materials are an interesting alternative to petrochemical products with potential application in almost all areas of human activity. Wishing to expand the field of cellulose acetate application to the biocomposite wood materials, the possibilities of cellulose isolation and its acetylation from two domestic, commercially meagrely used, wood species was investigated in this paper. Cellulose isolated from white willow (Salix alba) and black alder (Alnus glutinosa) was acetylated using acetic anhydride and perchloric acid catalyst, by treatment at room temperature for 45 minutes. Analysis of the laboratory acetylation process, beside chemical analysis of the gained product by infrared spectroscopy (FT-IR), indicated the impact of hemicelluloses, present both in cellulose and cellulose acetate structure, on values of mass increase, number of acetyl groups and the degree of substitution. Results of thermogravimetric analysis (TGA) later confirmed the statement that thermal properties of cellulose acetate were also dependant on hemicelluloses.
A new copper complex, trans-diaqua-trans-bis [1-hydroxy-1,2-di (methoxycarbonyl) ethenato] copper (abbreviation Cu(II) complex), was synthesized and its plant growth regulation properties were investigated. The results show a sharp dependence of growth regulation activity of the Cu(II) complex on the type of culture and its concentration. New plant growth regulator accelerated the development of the corn root system (the increase in both length and weight) but showed a smaller effect on the development of the wheat and barley root systems. Stimulation of corn growth decreased with increasing Cu(II) complex concentration from 0.0001% to 0.01% (inhibition at high concentrations—0.01%). The development of corn stems was also accelerated but to a lesser extent. Chitosan-coated calcium alginate microcapsules suitable for delivery of Cu(II) complex to plants were prepared and characterized. Analysis of the FTIR spectrum showed that complex molecular interactions between functional groups of microcapsule constituents include mainly electrostatic interactions and hydrogen bonds. Microcapsules surface exhibits a soft granular surface structure with substructures consisting of abundant smaller particles with reduced surface roughness. Release profile analysis showed Fickian diffusion is the rate-controlling mechanism of Cu(II) complex releasing. The obtained results give new insights into the complexity of the interaction between the Cu(II) complex and microcapsule formulation constituents, which can be of great help in accelerating product development for the application in agriculture
In the present study, the influence of adding natural fillers to a cellulose acetate (CA) matrix, in order to develop biocomposites, on the properties of the achieved materials has been investigated. Extracted wood flour, holocellulose, and alpha cellulose were used as appropriate fillers. The results of the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) of the fillers and biocomposites suggested the importance of the degree of degradation of filler properties, induced by the chemical treatment necessary for the preparation of the fillers, with emphasis on the content of lignin and the degradation of cellulose. Scanning electron microscopy (SEM) and mechanical analysis revealed that the matrix-filler ratio had a major effect on the prepared CA-based biocomposites, since polarity differences between the two major components caused the reduction of attractive forces in the matrix-filler relation, subsequently altering the properties of the developed materials.
Increasing demand for wood resulted in competition between different branches of wood-based production. High intensity production, like the production of wood-based panels, is forced to look for other lignocellulosic resources. Bark is a possible source for wood-based panel industry, especially for particleboards. Bark chips were crushed into bark dust, which were used for the production of single-layer particleboards. The share of bark dust was 0 %, 0.5 %, 1 %, 5 % and 10 %. The boards were tested on thickness swelling (immersion in water, exposure to humid conditions) and internal bond. The highest internal bond was determined in the particleboard with 1 % bark share. Thickness swelling of boards with added bark was higher compared to boards without bark. The highest swelling was observed in boards with 10 % bark dust (immersion in water) or 5 % (humid conditions). Bark based boards absorbed less water.
The paper gives an overview of chemical changes during heat treatment of wood and their influence on environment. Wood is one of the most used building materials because of its physical and technological properties. Various procedures improve its properties, and due to its environmental acceptability, heat treatment of wood is one of the most commonly used. Heat treatment causes changes in the cell walls and degradation of the main components of the wood structure (cellulose, hemicelluloses, lignin) and extractives. Hemicelluloses, as the most unstable components, are broken down first, followed by cellulose and finally lignin. Degradation results in a change in chemical composition and chemical reactions of colour change causing a technological problem because wood processing tends to make the colour as uniform as possible. The uniformity of colour and the desired colour tone are obtained by the process of steaming and thermal modification. The processing temperature is the most important factor that causes all the changes. Due to its wide use, need has arisen to investigate the ecological consequences of such a heat treatment process, as well as the impact of harmful substances and types of compounds released during the process and their toxicity.
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