Análise da madeira do Pinus oocarpa parte II: caracterização estrutural da lignina de madeira moída

Morais, Sérgio Antônio Lemos de; Nascimento, Evandro A.; Melo, Dárley Carrijo de

doi:10.1590/s0100-67622005000300015

Cited by 7 publications

(9 citation statements)

References 7 publications

(5 reference statements)

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“…Recently, the structure of Eucalyptus globulus lignins has been comprehensively studied at the University of Aveiro ( 14 , 16−18 ). In the early 1990s Piló-Veloso et al ( , ) summarized their studies on the structure of a E. grandis lignin using various wet chemistry methods as well as quantitative FTIR and 1 H NMR spectroscopic techniques. 13 C NMR was used, however, only in a semiquantitative mode.…”

Section: Introductionmentioning

confidence: 99%

Quantitative Characterization of a Hardwood Milled Wood Lignin by Nuclear Magnetic Resonance Spectroscopy

Capanema

Balakshin

Kadla

2005

J. Agric. Food Chem.

245

211

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The structure of Eucalyptus grandis milled wood lignin (MWL) was investigated by 2D 1H-13C HSQC, HMQC, and 1H-1H TOCSY correlation NMR techniques and by quantitative 13C NMR as well as by the permanganate oxidation degradation technique. The combination of 2D NMR and quantitative 13C NMR spectroscopy of nonacetylated and acetylated lignin preparations allowed reliable identification and calculation of the amount of different lignin structures. About 85% of side-chain moieties were estimated on the structural level. This information was substantiated by data on the quantity of various functional groups and interunit linkages as a whole. A modified method for calculation of the h:g:s ratio has been suggested and compared with previously suggested approaches. E. grandis MWL has been determined to have an h:g:s ratio of 2:36:62. The amounts of various phenolic/etherified noncondensed/condensed guaiacyl and syringyl moieties were approximately estimated. E. grandis MWL contained approximately 0.60/Ar of beta-O-4 moieties along with small amounts of other structural units such as pino/syringyresinol (0.03/Ar), phenylcoumaran (0.03/Ar), and spirodienone (0.05/Ar). The degree of condensation was estimated at approximately 21%; the main condensed structures are 4-O-5 moieties (approximately 0.09/Ar). The structure of E. grandis MWL was compared with those of other lignin preparations isolated from various hardwoods.

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Section: Introductionmentioning

confidence: 99%

Quantitative Characterization of a Hardwood Milled Wood Lignin by Nuclear Magnetic Resonance Spectroscopy

Capanema

Balakshin

Kadla

2005

J. Agric. Food Chem.

245

211

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“…(N.B. According to the literature the hydroxyl content in lignin may vary in the interval from 8 to 11 wt% [33]). This process was needed to establish a good proportion between the reactants, so that the esterification reactions conducted were using about 6 mL of methacrylic anhydride for each gram of lignin.…”

Section: Extraction Esterification and Characterization Of Ligninmentioning

confidence: 99%

“…NMR analysis of the natural lignin aimed at evaluating the different hydrogen protons present in the natural lignin, such as those related to aliphatic chains, aromatic rings and hydrogens metoxylic, aliphatic and phenolic [26,33]. The 1 H NMR spectrum provides important information regarding the hydroxyl groups present in the natural lignin molecule.…”

Section: Extraction Esterification and Characterization Of Ligninmentioning

confidence: 99%

Styrene/Lignin-Based Polymeric Composites Obtained Through a Sequential Mass-Suspension Polymerization Process

2017

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“…A celulose está embutida dentro de uma matriz de hemicelulose e lignina como mostrado na Figura 2. 3,26,25,27,28 Figura 2: Celulose rodeada por hemicelulose e lignina. Adaptada de Doherty et al…”

Section: Ligninaunclassified

“…Em sua forma natural não apresenta enxofre, fósforo, nitrogênio ou outros elementos. 31,34 Três estruturas formam a base da macromolécula da lignina: p-hidroxifenila 3,22,36,35,26 Os principais métodos são:…”

Section: Composição E Estruturaunclassified

Compósitos poliméricos obtidos pela combinação de estireno e lignina

Victor¹

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Lignin is a lignocellulosic materials-derived natural polymer with high availability, produced in large-scale, presenting a huge potential for production of new polymeric composites. Due to its complex macromolecular structure, and its low compatibility with styrene, eucalyptus wood-extracted lignin through modified Kraft method was esterified with methacrylic anhydrideexhibiting a yield of 64 %in order to ensure homogeneity in the organic phase into the reaction medium. The mass-suspension sequential polymerization process was employed in order to ensure adequate dispersion of lignin in the reaction medium. The evaluation of both the natural and esterified lignin through infrared (IR) spectroscopy showed a decrease of the hydroxyl band, characteristic of natural lignin (3200-3400 cm-1) and an increase of the characteristic ester band (1720 to 1740 cm-1). According to nuclear magnetic resonance (1 H NMR), intense peaks were observed in the range from 1.7 to 2.05 ppm (-CH 3) and 5.4 ppm to 6.2 ppm (=CH 2), related to methacrylic anhydride. According to the thermogravimetric analysis (TGA), esterified lignin showed a decrease in its thermal stability when compared to natural lignin, exhibiting two main weight losses between 200 °C and 300 °C and in the interval from 550 °C to 800 °C. Comparatively, the esterified lignin also displayed an increase in its glass transition temperature (Tg) for para 98 °C, related to natural lignin, whose Tg was determined to be equal to 91 °C. The polymer composites obtained by the combination of styrene and natural or esterified lignin, in a proportion of 5%, 10% and 20% of lignin, were successfully synthesized, presenting regular morphology. The incorporation of lignin (natural and modified) into the thermoplastic matrix of polystyrene (PS) led to a significant increase in the viscosity of polymer composites, in comparison to the one observed for the pure PS. Additionally, polymeric materials from viscosity essays were analyzed once more by thermal analysis (TGA and DSC), showing that the good thermal stability is kept, displaying weight losses lying in the interval from 350 °C e 480 °C. Particularly for the polymer composites containing modified lignin, the Tg was increased in comparison to pure PS, as a result of copolymerization between styrene and esterified lignin.

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Análise da madeira do Pinus oocarpa parte II: caracterização estrutural da lignina de madeira moída

Cited by 7 publications

References 7 publications

Quantitative Characterization of a Hardwood Milled Wood Lignin by Nuclear Magnetic Resonance Spectroscopy

Quantitative Characterization of a Hardwood Milled Wood Lignin by Nuclear Magnetic Resonance Spectroscopy

Styrene/Lignin-Based Polymeric Composites Obtained Through a Sequential Mass-Suspension Polymerization Process

Compósitos poliméricos obtidos pela combinação de estireno e lignina

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