•Total colour difference, the content of lignin and extractives increased with the temperature.•DP of cellulose, modulus of rupture, and lightness difference decreased with the ...treatment.•Temperatures ranging from 20 to 187°C formed a compact cluster in the multivariate space.•Chemical, mechanical and colour traits of thermally modified wood showed close relationships.
In several different branches of the wood industry heat treatment is a growing application as it changes the chemical, mechanical, physical and biological properties of wood. Investigations using wet chemical analyses, Fourier transform infrared spectroscopy, size exclusion chromatography, and CIELab colour system have been conducted to study the changes in Norway spruce wood subjected to temperature up to 270°C over a 30min time period. The results showed that mass loss (ML), total crystallinity index (TCI) of cellulose, total colour difference (ΔE∗), and the content of lignin and extractives increased with the temperature, whereas degree of polymerization (DP) of cellulose, modulus of rupture (MOR), modulus of elasticity (MOE), lightness difference (ΔL∗), and the content of holocellulose, cellulose and hemicelluloses all decreased with the thermal treatment. Relationships between temperature and the examined wood traits were all fitted by exponential curves. Power law relationships were found to fit the trends for DP of cellulose with ΔE∗, ΔL∗, and TCI of cellulose. Also found were power law regressions for the content of hemicelluloses with MOE, MOR, ΔL∗, and ML. Temperatures ranging from 20 to 187°C formed a compact cluster, clearly separated from the higher examined temperatures in the multivariate wood trait space.
Chemical composition and morphological properties of Norway spruce wood and bark were evaluated. The extractives, cellulose, hemicelluloses, and lignin contents were determined by wet chemistry ...methods. The dimensional characteristics of the fibers (length and width) were measured by Fiber Tester. The results of the chemical analysis of wood and bark show the differences between the trunk and top part, as well as in the different heights of the trunk and in the cross section of the trunk. The biggest changes were noticed between bark trunk and bark top. The bark top contains 10% more of extractives and 9.5% less of lignin. Fiber length and width depends on the part of the tree, while the average of these properties are larger depending on height. Both wood and bark from the trunk contains a higher content of fines (fibers <0.3 mm) and less content of longer fibers (>0.5 mm) compared to the top. During storage, it reached a decrease of extractives mainly in bark. Wood from the trunk retained very good durability in terms of chemical composition during the storage. In view of the morphological characteristics, it occurred to decrease both average fibers length and width in wood and bark.
The paper assesses the influence of the heat flux on spruce wood (Picea abies L.) behavior. The heat flux was performed at 15, 20, 25, and 30 kW·m−2. The fire-technical properties, such as the mass ...burning rate, charring thickness, charring rate, as well as the chemical composition (contents of the extractives, lignin, cellulose, holocellulose), of wood were determined. The highest burning rate of spruce wood of 0.32%·s−1 was reached at the heat flux of 30 kW·m−2. The charring rate ranged from 1.004 mm·min−1 (15 kW·m−2) to 2.016 mm·min−1 (30 kW·m−2). The proposed model of the charring process of spruce wood in time and appropriate thickness as a selected parameter is applicable in validation of the results of computer fire models in the design of fire protection of wooden buildings. The decrease in the holocellulose content mostly caused by the degradation of hemicelluloses was observed during thermal loading. The biggest decrease in hemicelluloses (24.94%) was recorded in samples loaded at 30 kW·m−2. The contents of cellulose increased due to the structural changes (carbonization and crosslinking), the content of lignin increased as well due to its higher thermal stability compared to saccharides, as well as the resulting lignin condensation.
The paper deals with the assessment of the age of oak wood (0, 10, 40, 80 and 120 years) on its fire resistance. Chemical composition of wood (extractives, cellulose, holocellulose, lignin) was ...determined by wet chemistry methods and elementary analysis was performed according to ISO standards. From the fire-technical properties, the flame ignition and the spontaneous ignition temperature (including calculated activation energy) and mass burning rate were evaluated. The lignin content does not change, the content of extractives and cellulose is higher and the content of holocellulose decreases with the higher age of wood. The elementary analysis shows the lowest proportion content of nitrogen, sulfur, phosphor and the highest content of carbon in the oldest wood. Values of flame ignition and spontaneous ignition temperature for individual samples were very similar. The activation energy ranged from 42.4 kJ·mol−1 (120-year-old) to 50.7 kJ·mol−1 (40-year-old), and the burning rate varied from 0.2992%·s−1 (80-year-old) to 0.4965%·s−1 (10-year-old). The difference among the values of spontaneous ignition activation energy is clear evidence of higher resistance to initiation of older wood (40- and 80-year-old) in comparison with the younger oak wood (0- and 10-year-old). The oldest sample is the least thermally resistant due to the different chemical composition compared to the younger wood.
This work evaluates the effect of using selected inorganic chemicals as the main components of waterborne wood preservative systems on the degradation of the cellulose constituent in wood from model ...samples. The polymeric properties of cellulose and the homogeneity of the degradation process primarily reflect very well the degree of cellulose deterioration. Whatman papers, as pure cellulose model samples, were impregnated with 10 different 5 wt% solutions of inorganic salts and distilled water and consequently subjected to wet-thermal accelerated aging (T = 85 °C, RH = 65%, for 30 days). The samples were then derivatized to cellulose tricarbanilates (CTCs) through two different procedures (by precipitation in a methanol-water mixture/by evaporation of pyridine from the reaction mixture) and finally analyzed using size exclusion chromatography (SEC). Chemically treated and aged cellulose samples showed different changes in the degree of polymerization (DP) and polydispersity (PD) in terms of untreated non-aged standard caused by different ongoing degradation reactions, such as dehydration, hydrolysis, oxidation, and crosslinking. In general, the lowest degradation rate after treatment by chemicals and after accelerated aging was observed in samples treated by borates, NaCl, and ZnSO
·7H
O. The greatest depolymerization after treatment and after accelerated aging was caused by sulphates containing NH
, Cu
, and Fe
cations, with aging by NH
Cl and (NH
)
HPO
-treated samples also leading to significant depolymerization. The higher DP values are linked to the precipitated method of CTC preparation, though not for chlorides and phosphates. PD is also generally higher in precipitated and aged samples and is heavily influenced by the presence of low molecular weight products. This paper brings new insights regarding the complex evaluation of the polymeric properties of degraded cellulose by considering all important factors affecting the sample and the analysis itself through the use of statistics. From the statistical point of view, the influences of all factors (solution, aging, method) and their interactions (except aging*method) on DP are statistically significant. The influence of the sample processing method used for analysis of the desired results becomes important mainly in practice. This work recommends the evaporation method for more accurate description of more degraded cellulose.
Particleboards containing waste rubber (tires and mixtures of isolators and carpets) filler were evaluated from the point of view of its flammability. The assessment of the utilization of these ...composites in the construction industry was analyzed through the determination of their spontaneous ignition temperatures, mass burning rate and calorific value. Based on the results of spontaneous ignition temperatures, similar values between particleboards and particleboards containing 10%, 15% and 20% of waste tires were obtained. The average time was from 298 s to 309 s and the average temperature was from 428.1 °C to 431.7 °C. For the mass burning rate, there were similar results between particleboards and particleboards containing 10% of waste tires and waste rubber. The time to initiation was 34 s and the time to reaching a maximal burning rate was from 66 s to 68 s. The calorimetry results showed similar properties for the calorimetric value and ash content in particleboards and particleboards containing 10% of waste tires and waste rubber. The calorific value was from 18.4 MJ·kg−1 to 19.7 MJ·kg−1 and the ash content from 0.5% to 2.9%.
This paper focuses on the changes in chemical structure and fiber morphological properties of spruce wood during 15 months of its storage in an open forest woodshed. From the chemical composition, ...the extractives, cellulose, holocellulose, and lignin content were determined. The pH value was measured on the wood surface using a contact electrode. Acetic and formic acid, saccharides (glucose, xylose, galactose, arabinose and mannose), and polymerization degree (PD) of cellulose were analyzed using the HPLC method. Fiber length and width were determined using a fiber tester analyzer. After 15 months of storage the content of both cellulose (determined by the Seifert method) and lignin did not change; the quantity of hemicelluloses decreased by 13.2%, due to its easier degradation and less stability compared to cellulose; and the pH value dropped by one degree. HPLC analyses showed a total decrease in the cellulose DP of 9.2% and in saccharides of 40.2%, while the largest decreases were recorded in the quantity of arabinose, by 72%, in the quantity of galactose, by 61%, and in the quantity of xylose, by 43%. Organic acids were not detected due to their high volatility during wood storage. The total decrease in average fiber length was 38.2% and in width was 4.8%. An increase in the proportion of shorter fibers, and a decrease in the proportion of longer fibers, was recorded. It can be concluded that fundamental changes occurred in the wood, which could affect the quality of further products (e.g., chips, pulp, paper, particleboards).
This article deals with the possibility of valorizing wood waste from grapevine cultivation of the varieties Pesecká leánka (white graft) and Frankovka modrá (red graft), grown in Slovakia. From the ...point of view of chemical composition, two methods (water and ethyl alcohol) were performed for the determination of extractives, acid-insoluble (Klason) lignin, and structural carbohydrates, and FTIR spectra of the grape samples were recorded. Mechanical strength, compression test parallel to the grain, and morphological properties (fiber length, width, and shape factor using a fiber tester) were carried out. The energy potential of grapevines was evaluated by determining the calorific value. According to the results, the relatively high content of carbohydrates (54.19%–55.27%) provides a prerequisite for acid or enzymatic hydrolysis to produce monosaccharides or second-generation bioethanol. FTIR spectra confirmed the higher content of lignin and cellulose in red grapes. The compression strength of grape cuttings (37.34 MPa—red; 32.34 MPa—white) was comparable to the strength of softwood species; hence, these wastes can be used for particleboard or fiberboard production. Average fiber length is comparable to non-wood species; thus, grape cutting can be used for pulp and paper production. The calorific value of grape cuttings ranged from 18.68 MJ·kg−1 (white) to 18.91 MJ·kg−1 (red), with pellets having 16.96 MJ·kg−1. The energetic potential of grape cuttings was comparable to that of other wooden materials; on the other hand, the ash content of pellets from grape cuttings (10.54%) greatly exceeded the limit given by the EN ISO 17225-1 standard, which is a significant disadvantage to pellets used for heating.
Waste tires (granulate) and selected plastics from the automotive industry were evaluated by using the tertiary (pyrolysis) and quaternary (calorimetry) recovering. Pyrolysis is proving to be an ...environmentally friendly alternative to incineration and inefficient landfilling. Currently, the main challenges for pyrolysis of plastic waste are unavailability and inconsistent quality of feedstock, inefficient and hence costly sorting, and last but not least insufficient regulations around plastic waste management. Waste plastics and tire materials were characterized by TG/DTG analysis, Py-GC/MS analysis and calorimetry. TG analysis of the investigated materials gives the typical decomposition curves of synthetic polymers. The tested samples had the highest rate of weight loss process in the temperature range from 375 °C to 480 °C. Analytical pyrolysis of the tested polymers provided information on a wide variety of organic compounds that were released upon thermal loading of these materials without access to oxygen. Analytical pyrolysis offers valuable information on the spectrum of degradation products and their potential uses. Based on the results of calorimetry, it can be stated that the determined calorific value of selected plastic and rubber materials was ranging from 26.261 to 45.245 MJ/kg depending on the ash content and its composition.
The wood-water interactions of modified beech wood (
L.) were studied. Specimens were thermally modified at 180 (TM
), 200 (TM
) and 220 °C (TM
), acetylated (Acet), and melamine formaldehyde (MF) ...resin (Mel) modified. Afterwards, the water vapour characteristics, i.e. water vapour sorption isotherms, equilibrium moisture content (EMC), dimensional stability of specimens conditioned at 30, 65 and 90% RH and liquid water characteristics, i.e. water absorption, maximum moisture content (MC), leachability and swelling kinetics, were determined and the results compared with reference (Ref) specimens. From the results, it is evident that the scale of wood-water interactions was highly dependent on the thermal modification temperature and type of chemical modification. The water vapour isotherms of thermally modified wood decreased, whereas more severe treatment exhibited more distinct reduction. The EMC values of the Mel and TM
specimens decreased only at high RH, whereas the most significant decrease, within the whole range of observation, was found in the Acet group. The maximum MC reduction was achieved by acetylation. As a consequence of swelling reduction, dimensional stability expressed as anti-swelling efficiency (ASE) was considerably improved. A relatively high initial linear-phase swelling rate was found for the Ref specimens, whereas modified wood exhibited comparatively slow and gradual swelling.
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