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Now showing items 1 - 16 of 23

  • Biobased and Sustainable Alternative Route to Long-Chain Cellulose Esters

    Jebrane, Mohamed   Terziev, Nasko   Heinmaa, Ivo  

    Fatty acid cellulose esters (FACEs), which have been identified recently as sustainable film materials, are conventionally synthesized by the use of the reaction with acyl chloride/anhydride pyridine in the presence of LiCl/N,N-dimethylacetamide. In this study, we have developed a new synthetic route to FACEs using a vinyl ester of long chain fatty acid, which is an excellent biobased and highly reactive reagent, for the functionalization of cellulose. The developed method involves the synthesis of the long aliphatic fatty acid vinyl ester via a transition-metal-catalyzed transvinylation reaction between vinyl acetate and the fatty acid, followed by its subsequent reaction with cellulose to yield FACEs. In this work, we have used vinyl oleate as a model precursor to introduce the fatty acid chain to cellulose. The covalent grafting of the fatty acid chain to the free hydroxyl groups of cellulose was achieved through potassium carbonate (K2CO3)-catalyzed transesterification of vinyl oleate in the presence of N-methyl pyrrolidone as solvent with low toxicity. Successful functionalization of cellulose was confirmed by FTIR, C-13 CP-MAS NMR, X-ray diffraction, and the thermogravimetric analysis. The results obtained showed that the functionalization efficiency of the cellulose increased with higher temperature and prolonged reaction times. The strategy proposed in the present work is an important step onward in terms of sustainability because the long-chain vinyl ester can be synthesized from a renewable and biobased source, and the toxic and corrosive chemicals commonly employed for cellulose esterification are avoided.
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  • Durability of Epoxi-Oil Modified and Alkoxysilane Treated Wood in Field Testing

    Panov, Dmitri   Terziev, Nasko  

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  • Comparative natural durability of five wood species from Mozambique

    Uetimane Junior, Ernesto   Raberg, Ulrika   Terziev, Nasko  

    The objective of this study was to evaluate the natural durability of five lesser-utilized wood species from Mozambique. Both laboratory methods and field tests were applied for assessing wood decay of muanga (Pericopsis angolensis), metil (Sterculia appendiculata), namuno (Acacia nigrescens), ncurri (lcuria dunensis), and ntholo (Pseudolachnostylis maprounaefolia). Laboratory tests involved soft-, brown-, and white-rot fungi and termites. Heart- and sapwood of ncurri and ntholo were exposed in above-ground field tests; additionally, all species were exposed to in-ground contact tests. The results indicated that namuno, muanga, ncurri, and ntholo are resistant to soft-, brown- and white-rot fungi and the termite species Reticulitermes grassea and Mastotermes darwiniensis. Comparatively, soft-rot caused more severe decay on the studied wood species than did basidiomycete fungi. The brown-rot fungi Coniophora puteana, Gloeophiyllum trabeum, and Postia placenta caused less decay on the tested species than did the white-rot Trametes versicolor. Metil was not resistant to any of the mentioned hazards. Therefore, this species is not recommendable for exterior use if untreated. (C) 2011 Elsevier Ltd. All rights reserved.
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  • Efficiency of Bio-Oil Against Wood Destroying Organisms

    Temiz, All   Alma, M. Hakki   Terziev, Nasko   Palanti, Sabrina   Feci, Elisabetta  

    In this study, it was aimed to determine the efficiency of bio-oils on wood-water relations, decay and insect resistance. Bio-oil was obtained by pyrolysis of Scots pine wood (Pinus sylvestris L.) using extruder type pyrolyzer at 450,550 and 600 degrees C. Scots pine sapwood was impregnated with different bio-oils and water absorption, fungicidal characteristic and resistance against Hylotrupes bajulus was investigated. FTIR spectral analysis showed that the main constituents of bio-oils are various phenolic compounds. High leachability of the bio-oils was also found by UV-Vis spectral analysis and is a drawback when the oils are used as wood protecting agents. The results indicated that the wood impregnated with these bio-oils showed lower water absorption than that of the control group. The hydrophobic characteristics of wood samples treated with full and empty cell process did not differ significantly although the oil uptake of samples treated with full cell process was significantly higher than that of the empty cell process. Decay test results against brown rot fungi (P. placenta) indicated that the samples impregnated with bio-oils had a mass loss of 7-10%, which is lower than the mass loss of the untreated wood samples. Samples treated with bio-oils showed resistance against Hylotrupes bajulus according to EN 47 standard, except samples treated with the light part of bio-oil obtained at 600 degrees C.
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  • Curing of wood treated with vinyl acetate-epoxidized linseed oil copolymer (VAc-ELO)

    Cai, Shengzhen   Jebrane, Mohamed   Terziev, Nasko  

    Scots pine sapwood was treated with a new formulation consisting of vinyl acetate (VAc) and epoxidized linseed oil (ELO) catalyzed by potassium persulfate to impart protection to wood. The effects of various curing temperatures, durations, and solution uptakes on dimensional stability (DS) and leachability were studied. The new formulation provided good anti-swelling efficiency (ASE) ranging from 35% to 47% with negligible leaching of the treating agent after four cycles of water soaking and oven drying (2%-2.5%). The extent of polymerization in wood was observed by FTIR-attenuated total reflectance (FTIR-ATR) by evaluation of the areas below typical IR bands as a function of curing temperature and time. Linear relationships were found with high R-2 values. The FTIR data of extracted samples were interpreted that chemical reactions took place between the resulting copolymer and wood components.
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  • Early soft rot colonization of Scots sapwood pine in above-ground exposure

    Raberg, Ulrika   Terziev, Nasko   Land, Carl Johan  

    The early colonization of Scots pine (Pinus sylvestris L) sapwood exposed above ground (staple bed) was studied. Two different types of exposures were used, one in an open field and the other in a shaded field. Decay type and degree of degradation due to soft rot and mass and strength loss of wood were correlated. Fungal species in Scots pine sapwood were identified by sequencing, using the fungal nuclear ribosomal DNA (nrDNA) after 24 months. The most abundant decay type found was soft rot, which also agreed with the mass loss (7-8%). Pine sapwood did not differ significantly between the two sites regarding the average mass loss during the time of exposure. The early colonization of wood by soft rot fungi together with mass loss indicates that this fungal type might be more common in above-ground conditions than recognized earlier. (C) 2007 Elsevier Ltd. All rights reserved.
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  • Industrial Thermowood (R) and Termovuoto thermal modification of two hardwoods from Mozambique

    Pockrandt, Michael   Jebrane, Mohamed   Cuccui, Ignazia   Allegretti, Ottaviano   Uetimane Jr, Ernesto   Terziev, Nasko  

    The study aimed at treating metil (Sterculia appendiculata K. Schum) and neem (Azadirachta indica A. Juss) timber from Mozambique under industrial conditions by steam [Thermowood (R) (TW)] and vacuum [Termovuoto (TV)] thermal modifications (TM). Matched boards were treated identically and wood alterations in chemistry, colour, mass loss (ML), mechanical properties and durability were compared. The applied vacuum partly removed the acetic acid that causes carbohydrate degradation, i.e. heat applied under vacuum was less destructive. TM under vacuum generated a lighter colour than that caused by steam treatment. ML was significantly higher after the TW process namely, 14.1 vs. 9.9% after thermovacuum treatment for metil and 14.2 and 12.1% for neem. Colour and ML changes correlated with the decrease in shear strength, rupture and elasticity moduli and increase in wood decay resistance. Metil wood is more permeable and demonstrated significant differences between the treatments; the thereto-vacuum process was less destructive but led to less improvement of durability compared to TW treatment.
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  • Dislocations in Norway spruce fibres and their effect on properties of pulp and paper

    Terziev, Nasko   Daniel, Geoffrey   Marklund, Ann  

    Wood "cell-wall deformation" is a comprehensive term describing any physical dislocation in the wall caused by mechanical forces. The development and effect of fibre dislocations on wood fibres, and their ultimate impact on the mechanical properties of paper remain rather obscure and controversial. Dislocations are difficult to quantify through a lack of defined measurable features, and research is aggravated by the inherent difficulties of applying statistical tools. A direct approach for studying the effect of dislocations on the mechanical properties of paper was used in this study. Dislocations in fibre cell walls were introduced by exposing whole wood fibres in mature and juvenile wood samples to compression stress. Sapwood samples of Norway spruce (Picea abies Karst.) were loaded by compression to their ultimate strength using an Alwetron-50 universal testing machine. Failure of samples conditioned to a moisture content of 9-15% always occurred in an oblique (relative to the fibre axis) plane and all fibres in the plane were deformed. When samples were loaded in a wet condition (i.e., moisture content close to the fibre saturation point), failure occurred at one end of the samples, resulting in highly disorganised fibres. Pulp and paper from the compressed fibres were produced and the mechanical properties of the paper were tested. Results of the mechanical tests were compared statistically to results derived from paper made from matched non-compressed control samples. Morphological features of fibres and dislocations after compression failure were characterised using microscopy (scanning electron microscopy, polarised light) on the whole wood and macerated fibres before and after paper testing. The above experimental approach showed that paper made from control samples had significantly better mechanical properties than paper made from samples loaded by compression under dry or wet conditions. At a tensile index of 90 N m/g, the tear index was measured as 23.6 mN m(2)/g for controls, while the corresponding values for compressed wet wood samples was 12.6 and 16.3 mN m(2)/g for samples at 9-15% moisture content. Paper made from juvenile wood also showed lower mechanical properties compared to controls. The results prove the negative effect of dislocations on the mechanical properties of paper in the worst case scenario and are of practical importance.
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  • The effect of (induced) dislocations on the tensile properties of individual Norway spruce fibres

    Eder, Michaella   Terziev, Nasko   Daniel, Geoffrey   Burgert, Ingo  

    Axial compressive stresses can cause distortion of the cellulose fibril alignment in the wood cell wall. These deformations are thought to occur in the living tree and/or to develop during wood processing and seem to adversely affect the mechanical properties of pulp and paper and other fibre-based products. To characterise the influence of dislocations on the mechanical properties of the unmodified cell wall, dislocations were artificially created by applying high compression loads to wood blocks parallel to the fibre axis. Mechanically isolated fibres containing different levels of dislocations were then subjected to tensile tests. Comparison between micromechanical properties of reference fibres and fibres that were artificially loaded in compression revealed the importance of dislocations for the mechanics of both earlywood and latewood. However, the tensile strength (decrease similar to 19% for earlywood and similar to 26% for latewood) was less affected than expected from structural observations of the pre-compressed zones.
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  • Comparative Study of Two Softwood Species Industrially Modified by Thermowood (R) and Thermo-Vacuum Process

    Jebrane, Mohamed   Pockrandt, Michael   Cuccui, Ignazia   Allegretti, Ottaviano   Uetimane, Ernesto, Jr.   Terziev, Nasko  

    Scots pine and Norway spruce, the most used commercial wood species in Europe, were thermally treated under industrial conditions by steam (Thermowood (R)) and vacuum (Termovuoto). Matched boards were treated, and the alterations in chemistry, color, mass loss, mechanical properties, and durability were compared. In treatments at identical temperature and duration, Thermowood (R) and the thermo-vacuum process caused similar mass loss in both wood species. The thermal treatments showed minor effects on the released acetic acid during the thermal degradation of polysaccharides. The equilibrium moisture content correlated well with the mass loss and confirmed indirectly the similarity of the two processes. The chemical composition and durability of the two groups of treated wood were similar. In conclusion, Thermowood (R) and thermo-vacuum treatments according to Termovuoto technology both produce similar final products with regard to chemical composition, physical-mechanical properties, and durability, with some differences in the appearance.
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  • Does copper tolerance provide a competitive advantage for degrading copper treated wood by soft rot fungi?

    Karunasekera, Hasanthi   Terziev, Nasko   Daniel, Geoffrey  

    The ability of soft rot fungi possessing strong (Phialophora malorum), medium (Phialophora mutabilis) and poor copper tolerance (Chaetomium globosum) to degrade untreated and CuSO4 and micronized copper treated birch- and pine wood was assessed using ENV 807 standard tests. The aim was to determine whether an ability to grow on Cu-agar and copper in liquid cultures can be transcribed into a competitive advantage to degrade Cu-treated wood. An ability to tolerate high copper levels in-vitro was not correlated with increased decay by the fungi but rather reflected the native chemistry of the wood cell walls. Both untreated and Cu-treated wood were degraded by the three fungi and showed aggressiveness in the order C. globosum > P. mutabilis > P. malorum Higher mass loss was recorded for birch than pine and decreased progressively as the copper loadings increased with statistically insignificant difference noted between Cu-treatments. Microscopy showed decay at the cell wall level to reflect degree of lignification with parenchyma cells degraded first in both untreated and Cu-treated wood. Results indicate presence of copper and its toxicity is unlikely to be the main reason for preventing soft rot decay of wood but rather the additive effect of copper binding to the wood material. (C) 2016 Elsevier Ltd. All rights reserved.
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  • Comparative Wood Anatomy and Chemical Composition of Millettia mossambicensis and Millettia stuhlmannii from Mozambique

    Uetimane, Ernesto, Jr.   Jebrane, Mohamed   Terziev, Nasko   Daniel, Geoffrey  

    The wood anatomy and chemistry of a relatively lesser used wood species, known in Mozambique as nsangala (Millettia mossambicensis J. B. Gillett), was compared to overexploited species jambire (Milletia stuhlmannii Taub.) to provide diagnostic features for safe discrimination. The anatomical results showed that both species shared several similarities such as intervessel pitting size range (8 mu m to 11 mu m), rays composed of only procumbent cells, fiber dimensions (average length up to 1359 mu m and wall thickness up to 10 mu m), and banded axial parenchyma. The extractives and lignin content were higher in jambire, while the carbohydrates and acetyl contents were higher in nsangala. The main anatomical feature separating the two species was the porosity pattern with semi-ring porous wood of nsangala compared to the diffuse-porous structure of jambire. Jambire had wider vessel lumina (200 mu m) and up to 3 vessels/mm(2) compared to nsangala vessel lumina of 86 mu m and a frequency of 37 vessels/mm(2).
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  • Comparative Wood Anatomy and Chemical Composition of Millettia mossambicensis and Millettia stuhlmannii from Mozambique

    Uetimane Jr., Ernesto   Jebrane, Mohamed   Terziev, Nasko   Daniel, Geoffrey  

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  • Effect of bio-oil and epoxidized linseed oil on physical, mechanical, and biological properties of treated wood

    Temiz, Ali   Kose, Gaye   Panov, Dmitri   Terziev, Nasko   Alma, Mehmet Hakki   Palanti, Sabrina   Akbas, Selcuk  

    In this article, the effects of bio-oil and epoxidized linseed oil (ELO) on water absorption, tangential swelling, decay and insect resistance, thermo-gravimetric analysis, and mechanical properties of treated wood samples were studied. The bio-oil used in this article was by-product of ThermoWood thermal modification process. Linseed oil and hydrogen peroxide were used to prepare ELO. The results indicated that the samples treated with bio-oil had lower water absorption than that of the control group. The second treatment with ELO significantly reduced further the water absorption. The decay resistance of treated wood samples with 20% of bio-oil against brown (Coniophora puteana) and white rot (Trametes versicolor) fungi was very high. According to the insect test results, increasing bio-oil concentration from 10% to 20% significantly decreased surviving rate of Hylotrupes bajulus. Thermo-gravimetric analysis showed that all treated samples had higher initial deterioration temperature than that of the control group. Regarding the wood strength, the impregnated bio-oil generally reduced the mechanical properties of wood except modulus of elasticity (MOE). (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1562-1569, 2013
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  • Effect of abnormal fibres on the mechanical properties of paper made from Norway spruce, Picea abies (L.) Karst.

    Terziev, Nasko   Daniel, Geoffrey   Marklund, Ann  

    The aim of the present study was to determine the effect of a variety of abnormal fibres on the mechanical properties of paper made from Norway spruce, Picea abies (L.) Karst. Fibres representing abnormality were obtained from trees treated by irrigation and fertilisation. Moreover, fibres from compression wood and its accompanying opposite wood were isolated. The effect of dislocations on paper quality was studied on four mixtures (20, 40, 60 and 80% fibres with induced dislocations) of untreated/compressed fibres. Two more groups consisting of control untreated samples and samples with 100%-induced dislocations were also included in the test. The mechanical properties of the paper were tested and the results were compared to those of control samples. Abnormal fibres reduced the desired mechanical properties of the final paper concerning tensile strength, modulus of elasticity and tear-tensile index. Irrespective of the type of treatment, all morphological changes introduced in fibre cell walls appear to directly affect changes in the mechanical properties of the paper. Control samples had a tear index of 25 compared to 10 mN m(2) g(-1) of samples containing 100% dislocations. It is obvious that 20% of dislocations, an amount that is expected to be induced in pulp under mechanical processing and transport, will contribute to a decrease in tear index with an average of 3 mN m(2) g(-1), i.e., 10% of the total value.
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  • Application of non-symmetrical drying tests for assessment of drying behaviour of ntholo (Pseudolachnostylis maprounaefolia PAX)

    Uetimane, Ernesto, Jr.   Allegretti, Ottaviano   Terziev, Nasko   Soderstrom, Ove  

    Experiments concerning drying behaviour of ntholo (Pseudolachnostylis maprounaefolia PAX) were conducted to find a suitable drying schedule. Two non-symmetrical drying (NSD) tests were carried out to determine the drying behaviour of ntholo in terms of drying rate and stress behaviour. A tentative drying schedule was selected for comparison of the test results with those of similar tests with other known species. The schedule was tested in a laboratory kiln on 28-mm thick boards. According to both NSD tests and laboratory tests, ntholo dries easily but slowly. The laboratory drying lasted 266 h and achieved standard drying quality characterised by 8.9% moisture content, a moisture gradient of 1.2% and a case-hardening (gap) of 1.2 mm. Twist was the largest deformation with 3.4 mm per 1000 mm on average. The assigned schedule provided standard drying quality and it could be tested further in industrial kilns.
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