Influence Of Hemicelluloses Research Articles

Lignocellulosic nanofibers from triticale straw: The influence of hemicelluloses and lignin in their production and properties

The present work aims to determine the influence of hemicellulose and lignin content in the production of lignocellulosic nanofibers (LCNF) from triticale straws. Triticale straws were digested and then gradually delignified, preserving as much hemicelluloses as possible. The obtained LCNF was characterized and used as paper strength additive, observing that hemicellulose and lignin have a key role on the final properties thereof, as well as on their reinforcing potential as paper additive, obtaining LCNF with the same paper reinforcing potential than CNF obtained by TEMPO ((2,2,6,6-Tetramethyl-piperidin-1-yl)oxyl) mediated oxidation.

Micromechanics of creep and relaxation of wood. A review COST Action E35 2004–2008: Wood machining – micromechanics and fracture

Abstract Wood, like all polymeric materials, shows viscoelastic behaviour. The time dependent behaviour of wood depends on material anisotropy, temperature, moisture and stresses. To predict the behaviour of wood, numerous mathematical models have been developed largely relying on experimental results. In this paper, time dependent viscoelastic behaviour of wood is reviewed under constant and cyclic climatic conditions, separately. More emphasis is given on results obtained in recent years on the behaviour of thin wood tissues, single fibres, thermo-viscoelasticity of wood, influence of hemicelluloses and the modelling of the effect of transient moisture at the molecular level on the mechanical response.

Influence of hemicelluloses on the structure and properties of Lyocell fibers

AbstractIn the present paper the difference in the structure and properties of Lyocell fibers with different hemicelluloses content was investigated. The supermolecular structure and the morphological characterization were compared. The fibril aggregation size was estimated by the cross‐polarization magic‐angle spinning carbon‐13 nuclear magnetic resonance (CP/MAS13C‐NMR) spectroscopy. Meanwhile, the difference in the mechanical, the fibrillation resistance and the dyeing properties of Lyocell fiber with different hemicelluloses content was also analyzed. POLYM. ENG. SCI., 47:702–706, 2007. © 2007 Society of Plastics Engineers.

The influence of hemicellulose on fibril aggregation of kraft pulp fibres as revealed by FE-SEM and CP/MAS 13C-NMR

Three Norway spruce pulps were produced using different kraft pulping methods, in order to obtain large differences in cellulose and hemicellulose proportions at a similar lignin content. The hemicellulose content in the three pulps varied between 10% and 22%. The aim of the study was to evaluate the influence of cellulose and hemicellulose on fibre ultrastructure and correlate this with the differences observed in the mechanical properties between the pulps. The ultrastructure of the pulp fibres were studied using Field Emission Scanning Electron Microscopy (FE-SEM) and Solid-State Cross Polarisation Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance (CP/MAS 13C-NMR) in combination with spectral fitting. CP/MAS 13C-NMR measured the average bulk properties of the pulp fibres, while FE-SEM allowed for observations on the ultrastructure of fibre surfaces. The ultrastructure of the fibres varied with varying hemicellulose content. The pulp with a high hemicellulose content had a porous surface structure. In fibres with a low hemicellulose content, the fibril aggregates (macrofibrils) formed a much more compact surface structure. With CP/MAS 13C-NMR this change was reflected by an increase in average fibril aggregate width with decreasing hemicellulose content. Results from FE-SEM and CP/MAS 13C-NMR correlated well. The changes recorded in ultrastructure may explain the very different mechanical properties reported previously for pulps with different hemicellulose content.

Influence of hemicelluloses on the aggregation patterns of bacterial cellulose

Cellulose from the bacteriumAcetobacter xylinum was used as a model system for investigating the influence of other cell wall polysaccharides on the aggregation of cellulose. The patterns of aggregation of the bacterial cellulose were modified when the cellulose was produced in the presence of hemicellulose-like saccharides. The celluloses were found to be more like the Iβ-type found in higher plant celluloses than the Iα-type in the control bacterial celluloses. The effects of isolation procedures on structure were also explored. It was found that the structures of isolated celluloses were influenced by the procedures used in isolation.

Hemicelluloses as structure regulators in the aggregation of native cellulose

The influence of hemicelluloses on the aggregation of cellulose in higher plant cell walls was modelled by adding hemicelluloses to cultures of the cellulose producer Acetobacter xylinum. Characterization of the celluloses by X-ray diffractometry showed them to be more like those that occur in higher plants; the coaggregation of the hemicelluloses suggests their occlusion within and between the crystalline domains of the celluloses. The authors propose that hemicelluloses may be primary moderators of the tertiary structure of cell wall celluloses, allowing the development of a wide range of properties.

パルプのハイポクロライト漂白に際してセルロースの酸化崩壊に及ぼすヘミセルロースの影響

パルプのハイポクロライト漂白に際してセルロースの酸化崩壊に及ぼすヘミセルロースの影響