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Pulp fibrillation results from refining and is of prime importance for papermaking. Yet a structural parameter reflecting the extent of fibrillation remains elusive. In this work, we demonstrate that in refined pulps, the interfibrillar distance at water saturated state (Ls), as derived from the interference factor from small angle X-ray scattering, structurally reflects fibrillation degree. Interestingly, the minimal L obtained at low water content is close to the crystal thickness derived from wide angle X-ray scattering. For a series of refined pulp samples, significant regressions are established between Ls and equilibrium moisture content, transmittance (T%), surface energy components (γLW, γAB), and the normalized crystallinity index (CrIn). These regressions establish Ls as a unique structural parameter for quantifying the fibrillation degree and derived properties of refined pulps without the need of a multi-parameter and time-consuming analyses. [ABSTRACT FROM AUTHOR]

Cellulose acetylation has been reported as a side reaction of cellulose treatment with the ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIm][OAc]) (Karatzos et al. in Cellulose 19:307-312, 2012) and other 1,3-dialkylimidazolium acetate ionic liquids. 1-Acetylimidazole (AcIm), an [EMIm][OAc] impurity, has been found to be the actual acetylating agent (Zweckmair et al. in Cellulose 22:3583-3596, 2015), and the degree of acetylation was relatively low, below a DS of approx. 0.1%. Higher degrees of cellulose acetylation (DS > 10%) have been observed when the entire wood was mixed with [EMIm][OAc] instead of cellulosic pulp only (Abushammala et al. in Carbohydr Polym 134:609-616, 2015). In this paper, we explore the impact of wood constituents, mainly lignin, on cellulose acetylation using AcIm. The results demonstrate that lignin itself can be readily acetylated upon mixing with AcIm, and-noteworthy-that lignin presence significantly accelerates cellulose acetylation. The initial rate of cellulose acetylation by AcIm increased from 1.8 to 4.7%/h when only 1% of lignin, based on cellulose mass, was added. A mechanistic study employing cellulose and lignin model compounds showed lignin to be more susceptible to acetylation than cellulose and to act as an intermediate acetyl group source for further cellulose acetylation in a catalytic scenario. [ABSTRACT FROM AUTHOR]

Lignin-coated cellulose nanocrystals (CNCs) were extracted from the tropical wood Angelim Vermelho in a yield of 47 % based on wood cellulose content. The procedure combined a mild steam explosion process with a treatment using 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]). The resulting CNCs showed exceptional aspect ratios of 83 ± 18 for wood-based CNCs and crystallinity index of 76 %. Residual lignin coating and cellulose acetylation were detected during the procedure and are proposed to minimize the known crystallite thickening. As a result, CNCs in dimensions close to their native state in wood were recovered. Furthermore, this novel extraction of CNCs directly from wood circumvents the tedious purification process necessary for CNC extraction from pulp. [ABSTRACT FROM AUTHOR]

The acetylating action of ionic liquids frequently used in biomass and polysaccharide processing, namely 1,3-dialkylimidazolium acetates, on cellulose has been studied. Analysis was based on an accurate method to quantify even minute amounts of organic acetates in polysaccharides. The acetylation is caused by impurities in the ionic liquids, specially purified ionic liquids do not show an acetylating effect. 1-Acetylimidazole has been proven to be the actual acetylating agent, and its presence in aged ionic liquids has been confirmed. Formation of the reagent, mechanism of its action-being an acetyl transfer rather than a typical esterification-kinetics of the acetylation and the effect of water in the system are studied in detail. The implications on processing of biomaterials in ionic liquids are discussed as well. [ABSTRACT FROM AUTHOR]

We report on the low efficiency of 1-butyl-3-methylimidazolium acesulfamate ([BMIM]Ace) at delignifying Norway spruce. A systematic kinetic and structural study of [BMIM]Ace pulping of spruce wood at 120 °C allowed shedding light on the structure of the reaction products and the nature of the reaction. In particular, wood residues and extracts were thoroughly characterized with a wide range of analytical techniques including H NMR, C NMR, P NMR, XRD, TGA, MS, FT-IR, conductivity, and elemental analysis. This extensive structural study evidenced prominent degradation of the acesulfamate anion into sulfate salts in lieu of the expected delignification. This unexpected behavior in view of previous reports of [BMIM]Ace pulping potency of wood is explained by extensive derivatization of minute lignin extracts with the sulfate salts, which can lead to an overestimation of delignification yields. [ABSTRACT FROM AUTHOR]

Cellulose I nanowhiskers were prepared in relatively high yield (48 ± 2 %) by single-stage hydrolysis of microcrystalline cellulose with an aqueous solution of 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim]HSO). This reaction occurred under mildly acidic reaction conditions with an [H]/[AGU] ratio of 0.24 mol/mol, i.e., 2 orders of magnitude lower than with concentrated sulfuric acid. The nanowhiskers exhibited small width and width distribution and also smaller length than nanowhiskers obtained with concentrated acid. With a relatively low content of sulfur they also exhibited higher thermal stability than whiskers obtained with concentrated sulfuric acid. The lower solvating power of the aqueous ionic liquid compared to that of concentrated sulfuric acid likely contributes to the greater hydrolysis efficiency in the present system. [ABSTRACT FROM AUTHOR]

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Bacterial cellulose/fibrin composites were treated with glutaraldehyde in order to crosslink the polymers and allow better match of the mechanical properties with those of native small-diameter blood vessels. Tensile and viscoelastic properties of the glutaraldehyde treated composites were determined from tensile static tests and cyclic creep tests, respectively. Glutaraldehyde-treated (bacterial cellulose) BC/fibrin composites exhibited tensile strength and modulus comparable to a reference small-diameter blood vessel; namely a bovine coronary artery. However, the breaking strain of the glutaraldehyde-treated composites was still well below that of the native blood vessel. Yet a long strain hardening plateau was induced by glutaraldehyde treatment which resembled the stress-strain response of the native blood vessel. Tensile cyclic creep test indicated that the time-dependent viscoelastic behavior of glutaraldehyde-treated BC/fibrin composites was comparable to that of the native blood vessel. Covalent bonding between BC and fibrin occurred via glutaraldehyde, affording mechanical properties comparable to that of the native small blood vessel. [ABSTRACT FROM AUTHOR]

series of resole-type phenolic resin-based nanocomposites, uniformly filled with cellulose nanowhiskers (CNWs), was successfully fabricated via direct solution mixing, then solvent-exchange with DMF and finally stepwise thermal curing. Dynamic mechanical analysis evidenced a moderate reinforcing effect with a minimum CNWs weight content of 5.0 wt% especially above the resin glass transition temperature ( T). The Halpin-Kardos model provided a good description of the CNWs reinforcing effect, suggesting perhaps the contribution of whiskers/matrix interactions rather than that of whiskers/whiskers interactions. Differential scanning calorimetry (DSC) further indicated that the nanowhiskers enhanced the resin cure, resulting in a more extensive degree of cure. Finally, the CNWs were found to only slightly lower the thermal stability of PF resins. In spite of a modest reinforcing effect, it is proposed that CNWs are also interesting fillers for high modulus and high T thermosetting resins that require high temperature cure. [ABSTRACT FROM AUTHOR]

BC/fibrin composites having fibrin/BC weight percent ratios ranging from 2/98 to 64/36 were produced by immersing never-dried-BC into varying compositions of fibrin/ionic liquid/DMSO solutions and for increasing time periods. The composite compositions were predicted from an FTIR/Beer's law calibration method based on calibration samples which exhibited an RMSEP of 2.5 weight percent. Observations of the composite surface with atomic force microscopy and of the internal pore structure with scanning electron microscopy showed that increasing immersion times resulted into smoother surface composites and allowed further infiltration of fibrin into the microporous structure of BC. Tensile strength and cyclic creep tests demonstrated that the composition had significant impact on the ultimate tensile stress and cyclic creep strain level of BC/fibrin composites. It is proposed that these composites have potential for artificial blood vessel applications. [ABSTRACT FROM AUTHOR]

The dynamics and interactions of a wood powder/phenol–formaldehyde (PF) resin composite are evaluated by solid-state 13C NMR. A 13C labeled and perdeuterated PF resin, with low molecular weight distribution, is synthesized and cured in the neat state and also in combination with yellow-poplar wood powder. The 13C NMR spectral features and cross-polarization dynamics of the PF hydroxymethyl and methylene nuclei are compared in the neat resin and in the wood powder composite. In the composite, a downfield shift of the PF hydroxyl bearing carbons suggests secondary interactions between the PF resin and wood. In addition, the PF resin methylene and hydroxymethyl carbons exhibit slower CP dynamics compared to the neat resin. Lower resin CP rates in the composite indicate lower molecular rigidity of the resin in presence of wood compared to the neat cured PF resin. [ABSTRACT FROM AUTHOR]