36 research outputs found
Weathering properties of wood-plastic composites based on heat-treated wood and polypropylene
No full textOne-stage thermo-hydro treatment (THT) of hardwoods: an analysis of form stability after five soaking-drying cycles
No full textA newly developed thermo-hydro treatment (THT) for use in a one-stage heat treatment process was examined by focusing on the form stability-related properties of European aspen (Populus tremula), birch silver (Betula pendula), and gray alder (Alnus incana). In particular, wood specimens were subjected to THT in a saturated steam atmosphere in a pilot-scale autoclave heated between 140 and 180 degrees C for 1-3 h. Several parameters of untreated and treated samples after several soaking and drying cycles were compared, namely, the changes in the volumetric swelling, swelling in the radial and tangential directions, cell wall total water capacity, and anti-swelling efficiency (ASE). Due to repeated wetting in the cyclic water submersion-drying test, the original ASE of 73% decreased to 65% (180 degrees C for 1 h), and the original ASE of 33% decreased to 5% (140 degrees C for 1 h). Wood modified at 170 degrees C presented good results that were not significantly lower than wood treated at higher temperatures while consuming less energy to deliver ASE improvement and was selected as optimum. To increase the ASE by 1%, the amount of energy consumed was decreased by 41%, 39%, and 17% compared with the treatment regimes of 160 degrees C for 1 h, 160 degrees C for 3 h, and 180 degrees C for 1 h, respectively. The new THT regime led to improved long-term dimensional stability due to the cross-linking of cell wall polymers, which resulted in increased cell wall rigidity
Scanning UV microspectrophotometry as a tool to study the changes of lignin in hydrothermally modified wood
No full textThermal modification (TM) of wood has occupied a relatively narrow but stable niche as an alternative for chemical wood protection. There are different technological solutions for TM and not all details of their effects on wood tissue have been understood. The one-stage hydrothermal modification (HTM) at elevated vapour pressure essentially changes the wood's composition and structure. In the present paper, the changes in three hardwood lignins (alder, aspen, and birch) were observed within the cell wall by means of cellular UV microspectrophotometry. The lignin absorbances in the compound middle lamella (CML) of unmodified wood are 1.7- to 2.0-fold higher than those in the fibre S2 layer. The woods were modified in the temperature range from 140 to 180 degrees C, while in the lower temperature range (140 degrees C/1 h), the UV absorbances are little affected. Essential changes occur in the range of 160-180 degrees C and the UV data reflect these by absorbtion changes, while the absorbances at 278 nm rise with factors around 2 more in the S2 layer than in the CML. The absorbance increments are interpreted as polycondensation reactions with furfural and other degradation products of hemicelluloses with the lignin moiety of the cell wall.Latvian State Research Programme NatPro
Assessment of wood microstructural changes after one-stage thermo-hydro treatment (THT) by micro X-ray computed tomography
No full textThe microstructural changes in a selection of softwoods and hardwoods resulting from thermo-hydro treatment (THT) at 160°C were examined by means of a state-of-the-art micro X-ray computed tomography. A dedicated X-ray scanning and volumetric processing protocol was developed. All reconstructed volumes had an approximate voxel pitch between 0.8 and 1.2 μm3. The microstructures of the same needle-shaped specimens before and after THT were visualized, and the individual parameters (maximum opening and lumen volume) for various cell types were quantified and compared. The highest values of substance volume were recorded for the ash sapwood (81%) and spruce specimens (72%). After THT, a significant correlation was found between the mass loss determined by gravimetry and the X-ray volume loss. The largest change occurred in the lumen volume of several tissue components, such as libriform fibers, tracheids, and ray parenchyma. The average aspen fiber volume reduction after THT was 31%, a value 2.6 times higher than the volume reduction of the average vessels. The porosity of ash sapwood increased from 41 to 56%, whereas the porosity of birch decreased from 34 to 29%
STUDY OF THE STRUCTURE OF WOOD-RELATED BIOPOLYMERS BY SORPTION METHODS
No full textThe potentialities of different vapour sorption methods are analized for the investigation of the microstructure of wood sorbents (wood, cellulose and lignin) as a particular case of biopolymers. There are two important distinctions in the sorption behaviour of biopolymers from traditional rigid sorbents, namely, the dependence of the characteristics of the porous structure on the thermodynamic properties of the sorbate, and the manifestation of the sorption hysteresis over the whole region of the sorption–desorption isotherm. The reason for these distinctions is the low rigidity (low values of modulus of elasticity) of biopolymers, hence, their considerable deformability under the action of sorption forces, resulting in the cleavage of interstructural bonds. This process, manifesting itself phenomenologically as swelling, depends on the activity of the sorbate and results in the appearance of porosity and a new surface. The criterion for the activity of the sorbate is close values of the solubility parameters of the polymer and the sorbate. Inert substances are adsorbed on the surface of large morphological formations and characterise the intact structure of the sorbent, while active sorbates cause the swelling of these formations and penetrate them, which enables a study of the microstructure of sorbents. In the desorption process, the cleaved bonds are restored, blocking a part of the sorbate in the polymer’s structure, which results in the appearance of sorption hysteresis, not connected directly with the porous structure of the sorbent
Life cycle inventory for currently harvested birch roundwood
No full textThe knowledge of the environmental performance of different products and services is vital in the modern world because of the climate change and other environmental problems that we are facing. Life cycle assessment is a valuable tool that allows to determine the environmental performance and compare products and services with the same function. There is no doubt that the importance of forests is crucial in the environmental protection, despite that raw wood products (roundwood, pulpwood and fuelwood) are not carbon neutral as previously thought because of the human activities during forest management processes. Apart from climate change, production of raw wood products also contribute to other environmental impact categories: acidification, eutrophication, photochemical oxidant formation and abiotic resource depletion. Previous studies have shown that the life cycle inventory (LCI) data for raw wood products should be collected from the site-specific not from more generic sources because of the significant differences in several geography and technology related factors. However, less discussed are time-related factors, which should also be acknowledged especially because of the long growing time of trees. The main objective of the present study was to determine which forest management processes should be included in the LCI for currently harvested birch (Betula spp.) roundwood in Latvia and based on these results compile the required data for the LCI. The results of forest management history analysis showed that for currently produced birch roundwood only logging operations should be included in the system boundary. Subsystems such as seed production, seedling production and silvicultural operations were not practiced or had only minor impact due to low mechanization level in the past. By taking into account the time-related factors, the LCI was developed and can be used in further calculations of environmental impacts for different wood-based products that are manufactured from currently harvested birch roundwood
Novel Alkyd-Linseed Oil Emulsion Formulations for Wood Coatings
No full textIn this experiment an oil-in-water emulsion, suitable as a coating for wood surface protection, was obtained. The main components of this emulsion were linseed oil and an alkyd, mixed at a ratio of 1:2. The experiments were conducted to find a valid combination of solubilizing agents, capable of giving a stable emulsion. Several surfactants, obtained from different producers, were tested. The main factors considered were the nature of the surfactant and its hydrophilic-lipophilic balance (HLB). Our results confirmed that the most suitable surfactants were ethoxylated non-ionic types with a high HLB value, while surfactants based on the gemini technology showed a poor efficiency due to scarce solubility in water, which led to the separation of phases. Once the optimal emulsion composition was obtained, hydrothermally treated and untreated aspen wood samples were coated to evaluate the degree of coating absorption for two different substrates
Riflessi della corrente neodialettale nella narrativa contemporanea pugliese. Analisi sociolinguistica
No full textThe phenomenon of “neodialettalità” is examined from to perspectives. Initially the term was used to describe works of Italian poets in vernacular languages. Such choice of language was a result of Italian poets’ protest in 1960s against gradual disappearance of vernacular languages and cultural traditions inherent to them. Currently the phenomenon of “neodialettalità” is a consequence of revolutionary sociocultural changes which took place over the last 30-40 years. Those changes did make Italian commonly used but at the cost of vernacular languages which for decades have been pushed to the margin and considered to be a symbol of backwardness or social degradation. It should come as no surprise then that those languages degenerated (or degraded, went through a crisis – author’s comment) and as a result cultural values inherent to them did too. Currently we can observe in Italian society a desire to partly resurrect those traditions though popularization of vernacular languages in many aspects of social life: in literature, advertising, graffiti, newspapers, websites etc. In this paper the author analyses novels of two authors from Apulia region whose works, both in terms of language and sociopragmatics, refer to the phenomenon of “neodialettalità”.The phenomenon of “neodialettalità” is examined from to perspectives. Initially the term was used to describe works of Italian poets in vernacular languages. Such choice of language was a result of Italian poets’ protest in 1960s against gradual disappearance of vernacular languages and cultural traditions inherent to them. Currently the phenomenon of “neodialettalità” is a consequence of revolutionary sociocultural changes which took place over the last 30-40 years. Those changes did make Italian commonly used but at the cost of vernacular languages which for decades have been pushed to the margin and considered to be a symbol of backwardness or social degradation. It should come as no surprise then that those languages degenerated (or degraded, went through a crisis – author’s comment) and as a result cultural values inherent to them did too. Currently we can observe in Italian society a desire to partly resurrect those traditions though popularization of vernacular languages in many aspects of social life: in literature, advertising, graffiti, newspapers, websites etc. In this paper the author analyses novels of two authors from Apulia region whose works, both in terms of language and sociopragmatics, refer to the phenomenon of “neodialettalità”
Enhancing Thermally Modified Wood Stability against Discoloration
No full textThermal modification of wood has gained its niche in the production of materials that are mainly used for outdoor applications, where the stability of aesthetic appearances is very important. In the present research, spectral sensitivity to discoloration of thermally modified (TM) aspen wood was assessed and, based on these results, the possibility to delay discoloration due to weathering by non-film forming coating containing transparent iron oxides in the formulation was studied. The effect of including organic light stabilizers (UVA and HALS) in coatings as well as pretreatment with lignin stabilizer (HALS) was evaluated. Artificial and outdoor weathering was used for testing the efficiency of different coating formulations on TM wood discoloration. For color measurements and discoloration assessment, the CIELAB color model was used. Significant differences between the spectral sensitivity of unmodified and TM wood was observed by implying that different strategies could be effective for their photostabilization. From the studied concepts, the inclusion of the transparent red iron oxide into the base formulation of the non-film forming coating was found to be the most effective approach for enhancing TM wood photostability against discoloration due to weathering
