1,721,016 research outputs found
TRACHEID LENGTH - GROWTH RELATIONSHIPS OF YOUNG PINUS BRUTIA GROWN ON REFORESTATION SITES
No full textBrutia pine (Pinus brutia Ten.) reforestations have been successfully used for decades in restoration of degraded forest ecosystems in Greece. The future purpose of these reforestations might expand to include wood utilisation. This study provides information on tracheid length of juvenile brutia pine aged 14-22 years grown on good and medium sites in Northeastern Greece. In addition, relationships among ring width, latewood proportion, wood density, and tracheid length were evaluated by using Causal Correlation Analysis. Similar mean tracheid length values were found for good and medium sites. Radial variability of tracheid length was similar on the good and medium sites, showing the typical increase in the juvenile phase. On both site types, latewood proportion showed a strong and positive relationship with wood density. Unexpectedly and only on the good sites, a significant positive relationship was found between ring width and wood density. On the medium sites, tracheid length was negatively related to fast growth and positively to high wood density. Tracheid length on the good sites was correlated only with latewood proportion with a weak positive relationship. The overall results may provide opportunities to better understand the quality of small-dimension timber of brutia pine and to better utilise it
TRACHEID LENGTH - GROWTH RELATIONSHIPS OF YOUNG PINUS BRUTIA GROWN ON REFORESTATION SITES
No full textBrutia pine (Pinus brutia Ten.) reforestations have been successfully used for decades in restoration of degraded forest ecosystems in Greece. The future purpose of these reforestations might expand to include wood utilisation. This study provides information on tracheid length of juvenile brutia pine aged 14-22 years grown on good and medium sites in Northeastern Greece. In addition, relationships among ring width, latewood proportion, wood density, and tracheid length were evaluated by using Causal Correlation Analysis. Similar mean tracheid length values were found for good and medium sites. Radial variability of tracheid length was similar on the good and medium sites, showing the typical increase in the juvenile phase. On both site types, latewood proportion showed a strong and positive relationship with wood density. Unexpectedly and only on the good sites, a significant positive relationship was found between ring width and wood density. On the medium sites, tracheid length was negatively related to fast growth and positively to high wood density. Tracheid length on the good sites was correlated only with latewood proportion with a weak positive relationship. The overall results may provide opportunities to better understand the quality of small-dimension timber of brutia pine and to better utilise it
Wood-borne formaldehyde varying with species, wood grade, and cambial age
No full textWhile the formaldehyde issue primarily focuses on adhesive systems used in wood-based panels, natural wood itself contains detectable formaldehyde. Potentially, this wood-borne formaldehyde is emitted over time; therefore, even with wood alone no "zero emission" is evident. In this work, the variation of formaldehyde contents in important commercial wood species that are dried and converted to wood particles for wood-based panel production was studied. Furthermore, whether wood grade or juvenile vs. mature wood have any effect on the formaldehyde content was determined. Results indicate that formaldehyde varied up to 4-fold across commercial softwood and hardwood species, but remained at low concentrations (under 1 mg/100 g). Softwoods generally had higher formaldehyde contents than hardwoods, while wood grade seemed to have no effect. The differences between juvenile and mature wood, however, were much more expressed. The lowest formaldehyde content was seen with juvenile wood from beech (under 0.15 mg/100 g), and the highest concentration was found in mature pine wood (approximately 0.70 mg/100 g)
Wood-borne formaldehyde varying with species, wood grade, and cambial age
No full textWhile the formaldehyde issue primarily focuses on adhesive systems used in wood-based panels, natural wood itself contains detectable formaldehyde. Potentially, this wood-borne formaldehyde is emitted over time; therefore, even with wood alone no "zero emission" is evident. In this work, the variation of formaldehyde contents in important commercial wood species that are dried and converted to wood particles for wood-based panel production was studied. Furthermore, whether wood grade or juvenile vs. mature wood have any effect on the formaldehyde content was determined. Results indicate that formaldehyde varied up to 4-fold across commercial softwood and hardwood species, but remained at low concentrations (under 1 mg/100 g). Softwoods generally had higher formaldehyde contents than hardwoods, while wood grade seemed to have no effect. The differences between juvenile and mature wood, however, were much more expressed. The lowest formaldehyde content was seen with juvenile wood from beech (under 0.15 mg/100 g), and the highest concentration was found in mature pine wood (approximately 0.70 mg/100 g)
Ammonia vs. thermally modified timber—comparison of physical and mechanical properties
No full textGaseous ammonia treatments as well as thermal modification of timber are both applied to modify the surface colour of wood species. Physical and mechanical properties of solid wood after gaseous ammonia treatments have been so far scarcely investigated. Selected physical and mechanical properties, i.e., colour, equilibrium moisture content, wood density, bending strength, bending stiffness, and impact bending strength were investigated for oak, Norway spruce and Scots pine after gaseous ammonia treatment. Obtained data were compared with thermally modified timber data. While wood colour changes were comparable, most properties of the ammonia treated wood did not alter. There was no significant density change of ammonia treated wood; equilibrium moisture content changed moderately. Mechanical properties also remained within acceptable fluctuations. Results proved that gaseous ammonia treatment is a modification that improves the decorative value but has minimal effect on technologically relevant properties of solid wood. In contrast, property alterations of colour-equivalent thermally modified timber were much more pronounced, with possible limitations to some applications
Effect of surface modification of beech wood flour on mechanical and thermal properties of poly (3-hydroxybutyrate)/wood flour composites
No full textPoly (3-hydroxybutyrate) (PHB), a biodegradable polymer from the polyhydroxyalkanoate biopolyester class, was filled with 20% beech wood flour (WF) to form completely biodegradable films. In the present study, the influence of surface modification of wood flour was investigated on the interfacial adhesion of PHB/WF composites. In addition to a hydrothermal pretreatment, sodium hydroxide and stearic acid were used as surface modifiers. Direct measurement of interfacial adhesion was carried out by mechanical testing and dynamic mechanical analysis. Thermal properties, degree of crystallinity of PHB/WF composites were determined by differential scanning calorimetry. Effects of sodium hydroxide and stearic acid treatment on the adhesion of PHB/WF interface were feeble when no hydrothermal pretreatment was applied. Nevertheless, surface modifiers applied on hydrothermally pretreated WF significantly improved the WF/PHB interface adhesion.Austrian Science Fund FWF [L319-B16
FIBRILLATION OF FLAX AND WHEAT STRAW CELLULOSE: EFFECTS ON THERMAL, MORPHOLOGICAL, AND VISCOELASTIC PROPERTIES OF POLY(VINYLALCOHOL)/FIBRE COMPOSITES
No full textNano-fibrillated cellulose was produced from flax and wheat straw cellulose pulps by high pressure disintegration. The reinforcing potential of both disintegrated nano-celluloses in a polyvinyl-alcohol matrix was evaluated. Disintegration of wheat straw was significantly more time and energy consuming. Disintegration did not lead to distinct changes in the degree of polymerization; however, the fibre diameter reduction was more than a hundredfold, creating a nano-fibrillated cellulose network, as shown through field-emission-scanning electron microscopy. Composite films were prepared from polyvinyl alcohol and filled with nano-fibrillated celluloses up to 40% mass fractions. Nano-fibrillated flax showed better dispersion in the polyvinyl alcohol matrix, compared to nano-fibrillated wheat straw. Dynamic mechanical analysis of composites revealed that the glass transition and rubbery region increased more strongly with included flax nano-fibrils. Intermolecular interactions between cellulose fibrils and polyvinyl alcohol matrix were shown through differential scanning calorimetry and attenuated total reflection-Fourier transform infrared spectroscopy. The selection of appropriate raw cellulose material for high pressure disintegration was an indispensable factor for the processing of nano-fibrillated cellulose, which is essential for the functional optimization of products.Austrian Science Fund (FWF) [L319-B16]; COST [COST-STSM-E50-4325
FIBRILLATION OF FLAX AND WHEAT STRAW CELLULOSE: EFFECTS ON THERMAL, MORPHOLOGICAL, AND VISCOELASTIC PROPERTIES OF POLY(VINYLALCOHOL)/FIBRE COMPOSITES
No full textNano-fibrillated cellulose was produced from flax and wheat straw cellulose pulps by high pressure disintegration. The reinforcing potential of both disintegrated nano-celluloses in a polyvinyl-alcohol matrix was evaluated. Disintegration of wheat straw was significantly more time and energy consuming. Disintegration did not lead to distinct changes in the degree of polymerization; however, the fibre diameter reduction was more than a hundredfold, creating a nano-fibrillated cellulose network, as shown through field-emission-scanning electron microscopy. Composite films were prepared from polyvinyl alcohol and filled with nano-fibrillated celluloses up to 40% mass fractions. Nano-fibrillated flax showed better dispersion in the polyvinyl alcohol matrix, compared to nano-fibrillated wheat straw. Dynamic mechanical analysis of composites revealed that the glass transition and rubbery region increased more strongly with included flax nano-fibrils. Intermolecular interactions between cellulose fibrils and polyvinyl alcohol matrix were shown through differential scanning calorimetry and attenuated total reflection-Fourier transform infrared spectroscopy. The selection of appropriate raw cellulose material for high pressure disintegration was an indispensable factor for the processing of nano-fibrillated cellulose, which is essential for the functional optimization of products.Austrian Science Fund (FWF) [L319-B16]; COST [COST-STSM-E50-4325
Cytogenetic mapping and orientation of the rhesus macaque MHC
No full textApplying fluorescence in situ hybridisation (FISH), six cosmid clones of rhesus macaque origin containing the genes SACM2L, RING1, BAT1 and MIC2, MIC3, MICID, and MOG of the major histocompatibility complex (MHC) were localised to the long arm of the rhesus macaque chromosome 6 in 6q24, the orthologous region to human 6p21.3. Furthermore, centromere to telomere orientation of the rhesus macaque MHC as well as the internal order of the MHC genes tested are the same as in human. Fiber-FISH allows a rough estimate of distances between these MHC genes in the rhesus macaque, and, as in the human, the rhesus macaque MHC comprises about 3 to 4 Mb. Copyright (C) 2003 S. Karger AG, Base
Poly(lactide acid) Composites Reinforced with Fibers Obtained from Different Tissue Types of Picea sitchensis
No full textWood fibers vary in their properties across species, across trees of the same species, and within single trees. This work takes advantage of wood fibers reinforcing poly(lactic acid) composites that originate from different tissue types of the species Sitka spruce (Picea sitchensis). Fibers were prepared with high temperature thermo-mechanical processing (TMP) from juvenile, mature, and compression wood tissues of Sitka spruce. Composites were made by solution casting with subsequent hot-pressing. Thermal as well as mechanical properties were determined using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and tensile testing. The obtained results showed that the chemical and physical properties of different tissue-type Sitka spruce fibers have significant effects on the thermal and mechanical properties of the Polylactic acid (PLA)/Sitka fiber composites. To increase interfacial compatibility between the hydrophilic fibers and the hydrophobic polymer matrix, the fibers were treated with vinyltrimethoxysilane (VTMO), while PLA was modified with 4,4-methylene diphenyl diisocyanate (MDI). It was found that PLA/Sitka composites treated with VTMO and MDI exhibited improved thermal and mechanical properties, compared to the unmodified control. The work also demonstrates that there is potential to improve biobased composites by utilizing the natural variability of wood fibers. J Appl Polym Sci 114: 2616-2623, 2009
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