1,720,999 research outputs found
Degradation of wood veneers by Fenton reagents: Effects of 2,3-dihydroxybenzoic acid on mineralization of wood
No full textPine sapwood veneer strips were subjected to Fenton's reagent (hydrogen peroxide and iron ions) without and in the presence of the iron chelator 2,3-dihydroxybenzoic acid (DHBA). Incubation was carried out in water (unbuffered) and in acetate buffer in order to assess the effect of the oxidising systems on the weight loss and tensile strength loss as well as on the mineralisation of wood. A great amount of carbon dioxide was produced during the incubation and revealed that organic substances (wood, DHBA, and acetate buffer) were mineralized due to Fenton's reaction. The degree of oxidative wood degradation by Fenton's reagent was greater in the buffered solutions than in the aqueous solutions. DHBA accelerated the decomposition of H2O2 in the solution but reduced the loss in weight and tensile strength and the degrees of mineralization of wood as compared to the system without DHBA. (C) 2012 Elsevier Ltd. All rights reserved
A Comparative Study of Self-Assembled Superstructures from Cellulose Stearoyl Ester and Poly(Vinyl Stearate)
No full textEffects of hydrophobation treatments of wood particles with an amino alkylsiloxane co-oligomer on properties of the ensuing polypropylene composites
No full textIn this study an amino alkylsiloxane co-oligomer was used to treat the wood particles to weight percent gains of 1.5%, 4.5%, and 7.0%, respectively, and coupling effects on the properties of the ensuing wood polypropylene composites were determined. The n-propyl-trimethoxysilane (alkylsilane) and 3-amino-propyltriethoxysilane (aminosilane) were also used for comparison. Compared to composites filled with untreated particles, composites treated with co-oligomer exhibited greater reduction in both the rates of water uptake and dimensional swelling than those treated with the other two silanes. Both, the flexural- and Charpy impact strengths of the composites, were moderately reduced but the tensile strength increased up to 23% due to treatment with the co-oligomer. The different effects by the silanes were also evidenced by dynamic mechanical analysis and microscopy. These results show that use of the co-oligomer can create a highly hydrophobic composite and any improvement in the mechanical properties is comparable to that with aminosilane. (C) 2012 Elsevier Ltd. All rights reserved
Weathering of uncoated and coated wood treated with methylated 1,3-dimethylol-4,5-dihydroxyethyleneurea (mDMDHEU)
No full textScots pine (Pinus silvestris L.) sapwood panels were treated with a methylated 1,3-dimethylol-4,5-dihydroxyethyleneurea (mDMDHEU) causing weight gains of approx. 25% and were exposed to weathering for 18 months. Compared to untreated panels, treatment with mDMDHEU reduced surface discoloration mainly caused by staining fungi. Panels treated with mDMDHEU clearly exhibited lower moisture content throughout the exposure time and lower water uptake in periodical submersion tests. The treatment also reduced deformation ( cupping) and crack formation of the panels due to weathering ( assessed as waviness and surface roughness). When coated panels were compared, a pre-treatment with mDMDHEU resulted in lower water uptake in periodical submersion tests, less discoloration, minor deformation ( cupping) and less crack formation ( assessed as waviness and surface roughness). Oil-based coatings did not peel off the mDMDHEU treated panel surfaces as observed for the untreated panel surfaces
Coating performance of finishes on wood modified with an N-methylol compound
No full textThis study describes the effects of wood modification with modified 1,3-dimethylol-4,5-dihydroxyethyleneurea (mDMDHEU) on the coating performance of solvent- and water-borne finishes. Although the basic colour of wood was slightly changed due to the modification, modified and unmodified samples did not display any colour differences after coating with translucent stains. Blocking of coated wooden substrates (degree of adhesiveness) was dependant on the type of finish system and, in a few cases, on the wood substrate. For all wood substrates, both treated and untreated, solvent-borne alkyd finish penetrated into the surface layers of the wood cells, while water-borne acrylic finishes spread only on the wood surfaces. The solvent-borne alkyd finish dried much more slowly on wood substrates than did the water-borne acrylics. Modification with mDMDHEU did not affect the drying rates of the finishes tested. The wet adhesion depended on the finish systems tested and on the pre-treatment of the wooden substrate. With regard to the pre-treatment, wet adhesion of one water-borne and the solvent-borne finish systems was significantly enhanced through precedent modification with mDMDHEU. The other two water-borne finish systems showed a higher degree of wet adhesion. This study demonstrates that modification of the wood substrate with mDMDHEU is compatible with both water-borne and solvent-borne finish systems and improves their wet adhesion on the wood surface. (C) 2006 Elsevier B.V. All rights reserved
Effects of modification with glutaraldehyde on the mechanical properties of wood
No full textScots pine (Pinus sylvestris L.) sapwood was treated with glutaraldehyde (GA) and magnesium chloride (MgCl(2)) as a catalyst. The effects of treating conditions on the mechanical properties were examined. The weight percent gain (WPG) of thin veneer strips after leaching was highest at pH 4.0-4.5 and tensile strength measured in zero-span strength and finite-span strength decreased with decreasing pH in a range of 3.5-5.5. Sole treatment with MgCl(2) also gradually decreased the tensile strength up to 25% with decreasing pH. At a fixed GA concentration (1.2 M), increasing MgCl(2) concentration linearly diminished tensile strength. Conversely, increasing GA at a fixed MgCl(2) concentration (1.5%) displayed the same effect, whereas in both cases zero-span strength loss was higher than finite span-strength loss. GA treatment of Scots pine sapwood stakes did not affect the modulus of rupture and the modulus of elasticity, but significantly reduced work to maximum load in bending and impact bending strength indicating embrittlement of wood. At the same time, compression strength increased with increasing WPG of GA. It is assumed that embrittlement caused by hydrolysis and crosslinking of cell wall polymers is compensated by enhanced compression strength thereby resulting in unchanged bending strength.German Academic Exchange Service (DAAD
Degradation of chemically modified Scots pine (Pinus sylvestris L.) with Fenton reagent
No full textThe Fenton reaction is supposed to play a key role in the initial wood degradation by brown rot fungi. Wood was modified with 1,3-dimethylol-4,5-di-hydroxyethyleneurea (DMDHEU) and glutaraldehyde (GA) to various weight percentage gains in order to study if these types of modifications are able to reduce wood degradation by Fenton reagent. Veneers modified with higher concentrations (1.2 and 2.0 mol l(-1)) of both chemicals exhibited minor losses in mass and tensile strength during treatment with Fenton reagent, which shows restrained oxidative degradation by hydroxyl radicals. The decomposition rate of H2O2 was lower in the Fenton solutions containing modified veneers than in those containing unmodified controls. More CO2 evolved in systems containing unmodified veneers than in systems with modified veneers, indicating that modification protected wood from mineralisation. The reason for the enhanced resistance of modified wood to the Fenton reaction is attributed to impeded diffusion of the reagent into the cell wall rather than to inhibition of the Fenton reaction itself. The results show that wood modification with DMDHEU and GA is able to restrain the degradation of wood by the Fenton reaction and can explain why modified wood is more resistant to brown rot decay
The fungal resistance of wood modified with glutaraldehyde
No full textAbstract
Scots pine sapwood (Pinus sylvestris L.) and European beech wood (Fagus sylvatica L.) were treated with glutaraldehyde (GA) in aqueous solution in the presence of magnesium chloride as a catalyst to evaluate the durability improvement towards staining and rot fungi. The GA modified specimens were dipped in a spore suspension of the blue stain fungus Aureobasidium pullulans and incubated for 8 weeks. The growth on both pine and beech wood was restrained, when the weight percent gain (WPG) of the specimens was above 7%. Under this condition, GA-modified beech wood did not suffer any mass loss after incubation with the white rot fungus Trametes versicolor. The threshold to prevent decay of beech and pine specimens towards the brown rot fungus Coniophora puteana was at a WPG of only 3%. GA treatment to a WPG over 6% protected the Scots pine stakes from soft rot decay during 32 weeks’ exposure according to ENv 807 (2001).</jats:p
Effects of chemical modification with glutaraldehyde on the weathering performance of Scots pine sapwood
Full text linkScots pine sapwood was treated with glutaraldehyde (GA) in aqueous solution using magnesium chloride as a catalyst in order to evaluate the durability towards weathering. Infrared spectroscopy suggested that GA treatment increased the photo-stability of lignin during artificial weathering of micro-veneers in a QUV over 168 h; photo-protection increased with increasing GA concentration. In comparison with the unmodified controls, GA-modified pine micro-veneer strips exhibited a lower tensile strength loss measured in a zero-span mode in the course of weathering. During 18 months of outdoor exposure, GA-modified pine wood boards exhibited a lower moisture content and water uptake than the unmodified ones. GA treatment also clearly restricted the penetration of blue stain fungi into deeper layers of wood. On the macroscopic scale, the surface of the GA-modified boards was significantly smoother due to less erosion, cracking and minor peeling of tracheids. Scanning electron microscopy further revealed that individual tracheids were detached from the cell compound and then washed away from the unmodified wood surface, whereas tracheids on surfaces of GA-modified wood remained in the tissue compound but displayed many axial and transversal cracks
Functional nanomaterials through esterification of cellulose: a review of chemistry and application
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