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Now showing items 1 - 16 of 20

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

    Jebrane, Mohamed   Terziev, Nasko   Heinmaa, Ivo  

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  • 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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  • 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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  • Genetic variation of biomass recalcitrance in a natural Salix viminalis (L.) population

    Ohlsson, Jonas A.   Hallingback, Henrik R.   Jebrane, Mohamed   Harman-Ware, Anne E.   Shollenberger, Todd   Decker, Stephen R.   Sandgren, Mats   Ronnberg-Wastljung, Ann-Christin  

    BackgroundSalix spp. are high-productivity crops potentially used for lignocellulosic biofuels such as bioethanol. In general, pretreatment is needed to facilitate the enzymatic depolymerization process. Biomass resistance to degradation, i.e., biomass recalcitrance, is a trait which can be assessed by measuring the sugar released after combined pretreatment and enzymatic hydrolysis. We have examined genetic parameters of enzymatic sugar release and other traits related to biorefinery use in a population of 286 natural Salix viminalis clones. Furthermore, we have evaluated phenotypic and genetic correlations between these traits and performed a genomewide association mapping analysis using a set of 19,411 markers.ResultsSugar release (glucose and xylose) after pretreatment and enzymatic saccharification proved highly variable with large genetic and phenotypic variations, and chip heritability estimates (h(2)) of 0.23-0.29. Lignin syringyl/guaiacyl (S/G) ratio and wood density were the most heritable traits (h(2)=3D0.42 and 0.59, respectively). Sugar release traits were positively correlated, phenotypically and genetically, with biomass yield and lignin S/G ratio. Association mapping revealed seven marker-trait associations below a suggestive significance threshold, including one marker associated with glucose release.ConclusionsWe identified lignin S/G ratio and shoot diameter as heritable traits that could be relatively easily evaluated by breeders, making them suitable proxy traits for developing low-recalcitrance varieties. One marker below the suggestive threshold for marker associations was identified for sugar release, meriting further investigation while also highlighting the difficulties in employing genomewide association mapping for complex traits.
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  • A new process for the esterification of wood by reaction with vinyl esters

    Jebrane, Mohamed   Sebe, Gilles  

    A novel route to wood modification by transesterification of vinyl esters is developed in the current study. The reaction between varied saturated and unsaturated vinyl esters and the hydroxyl groups of maritime pine sapwood (Pinus pinaster Soland) was examined using potassium carbonate as a catalyst. The esterification of wood was investigated by weight percent gain calculations (WPG), Fourier-transform infrared spectroscopy (FTIR) and (13)C cross-polarization with magic-angle spinning nuclear magnetic resonance spectroscopy ((13)C CP-MAS NMR). Differences in the rates of modification were noted, depending on the vinyl ester used, but relatively high yields were obtained in all cases. The infrared and NMR spectra of the different esterified samples were analysed in detail and the assignment of the signals corresponding to the grafted acyl groups confirmed that esterification occurred. (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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  • A novel simple route to wood acetylation by transesterification with vinyl acetate

    Jebrane, Mohamed   Sèbe, Gilles  

    A novel method for the acetylation of wood was investigated and compared with the classical method based on acetic anhydride. The transesterification reaction between vinyl acetate (VA) and hydroxyl groups of maritime pine sapwood (Pinus pinaster Soland) was performed in the presence of potassium carbonate as a catalyst and led to acetylated wood in high yield. The transesterification reaction was confirmed by FTIR and C-13 CP-MAS NMR spectroscopy. The efficiency of the VA transesterification increased with increasing temperature, reaction time, and catalyst amount, but a significant weight percentage gain (WPG) was obtained after only 3 h at 90 degrees C.
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  • Natural durability of selected larch and Scots pine heartwoods in laboratory and field tests

    Jebrane, Mohamed   Pockrandt, Michael   Terziev, Nasko  

    Highlights • We compared the natural durability of selected larch and Scots pine heartwoods. • The study was based on standard in- and above ground tests lasting 12 years. • Siberian larch from Siberia was the most durable among the studied heartwoods. • No relationship between natural durability and water absorption behavior of heartwoods. • Strong correlation to the total amount of extractives was observed. Abstract The aim of this study was to compare natural durability of Siberian larch heartwood grown in Siberia and Sweden as well as European larch and Scots pine heartwood grown in Sweden. The study was based on standard in- and above ground tests lasting 12 years but laboratory decay tests with white and brown rot fungi was also included. Field test results showed that Siberian larch heartwood from Siberia was the most durable among the studied heartwoods with a decay index of 60 after 12 years in Simlångsdalen (Sweden), while European larch heartwood grown in Sweden, was decayed to failure before the end of the test. Scots pine heartwood was found to perform similarly to Siberian larch from Siberia. No relationship could be established between natural durability of examined heartwoods and their water absorption behavior; however, strong correlation to the total amount of extractives was observed. Scots pine and Siberian larch heartwood from Siberia had 12.7 and 19.6% total extractives content respectively but the extractives composition differs. The study revealed also that lignin and monosaccharide content could not explain the variations in decay resistance of the studied heartwoods. No similarities in the natural durability revealed by laboratory and field tests were observed.
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  • A comparative study on the acetylation of wood by reaction with vinyl acetate and acetic anhydride

    Jebrane, Mohamed   Pichavant, Frederique   Sebe, Gilles  

    A comparative study on the acetylanon of maritime pine wood by reaction with vinyl acetate (VA) and acetic anhydride (AA) has been undertaken The reactivity of wood cellulose and lignin with regards to VA or AA was examined using different techniques The products dissolved in the reaction medium after acetylation of wood by the two different methods were analyzed by HPLC chromatography Results suggested that the cellulose sites in wood were more attacked by VA than by AA in our experimental conditions Besides the unreacted cellulose sites of the AA-acetylated sample could be further esterified by vinyl propionate which C-13 NMR signals could be differentiated from the acetyl signals The esterified materials obtained after modification of isolated cellulose and lignin were also characterized by FTIR C-13 CP-MAS NMR and P-13 NMR spectroscopy and compared Results indicated that VA could acetylate both biopolymers but they also showed that AA reacted more readily with lignin than VA Moreover FTIR spectroscopy revealed that unexpected side reactions concurrently occurred in lignin when VA was used It is hypothesized that some C-acetylation also took place between VA and a number of lignin aromatic rings during the treatment (C) 2010 Elsevier Ltd All rights reserved
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  • Synthesis and characterization of new vinyl acetate grafting onto epoxidized linseed oil in aqueous media

    Jebrane, Mohamed   Cai, Shengzhen   Panov, Dmitri   Yang, Xi   Terziev, Nasko  

    Modified poly (vinyl acetate) copolymers with epoxidized linseed oil (ELO) as co-monomer have been prepared. The polymerization was performed in aqueous medium without any additional protective colloid in the presence of sodium persulfate as catalyst. The effect of vinyl acetate (VAc)/ELO feed ratio, reaction temperature, reaction time, and catalyst amount has been studied. FTIR spectroscopy showed that the reaction between ELO and VAc resulted in slight decrease and shift in ELO characteristic bands of oxirane groups; and new bands were detected in the copolymer spectra attributed to PVAc and ELO functional groups. Moreover, new signals attributable to the copolymer were observed in the H-1 NMR spectra ( 4.07 and 1.62 ppm) and in the C-13 NMR spectra ( 15.29 and 31.0 ppm). Analysis by differential scanning calorimetry (DSC) showed a single T-g for the copolymerization product of VAc and ELO and two T-g for the PVAc/ELO blend, indicating the chemical reaction between VAc and ELO. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42089.
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  • Covalent fixation of boron in wood through transesterification with vinyl ester of carboxyphenylboronic acid

    Jebrane, Mohamed   Heinmaa, Ivo  

    Vinyl ester of 4-carboxyphenylboronic acid has been synthesized and tested as reactive reagent for permanent fixation of boron in wood based on an improved approach described previously. The essence of the method is a covalent incorporation of the boron compound via transesterification between wood hydroxyl groups and vinyl ester containing boron. The synthesis of this vinyl ester was accomplished by exchange reaction of vinyl acetate with 4-carboxyphenylboronic acid. The obtained vinyl ester of carboxyphenylboronic acid was characterized by FTIR and H-1-, and C-13-NMR spectroscopy. The covalent fixation of boron to wood's hydroxyl groups was achieved through potassium carbonate (K2CO3) catalyzed transesterification of the vinyl ester containing boron. The transesterification was confirmed by weight percentage gain (WPG) calculation, curcumin staining, FTIR, and C-13 CP-MAS NMR spectroscopy. The efficiency of the reaction improved with increasing temperature and reaction time.
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  • Covalent fixation of boron in wood through transesterification with vinyl ester of carboxyphenylboronic acid

    Jebrane, Mohamed   Heinmaa, Ivo  

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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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  • 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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  • Novel hydrophobization of wood by epoxidized linseed oil. Part 1. Process description and anti-swelling efficiency of the treated wood

    Jebrane, Mohamed   Fernández-Cano, Víctor   Panov, Dmitri   Terziev, Nasko   Daniel, Geoffrey  

    The known method of wood modification by epoxidized linseed oil (ELO) has a limiting practical application due to the rapid polymerization of ELO in the presence of acetic acid (AA) needed as a catalyst. The present study was designed to develop an alternative method by means of a two-step process to avoid the rapid polymerization. The treatment options were tested on Scots pine sapwood, with the dimensional stability (DS) of the treated samples in focus. The new method provided an anti-swelling efficiency (ASE) in the range of 40-57%, which was even better than the thermally modified (TM) reference samples with 40% ASE. The developed two-step process is a feasible and practical approach for ELO treatment of wood.
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