Abstract: Inverse gas chromatography (IGC) was used to determine the dispersive component of the free energy as well as the acid-base properties of cellulose fibre surfaces, before and after modification by corona treatment. It was found that the corona treatment increases both the dispersive contribution to surface energy and its acidic character, whereas only a slight increase in its basicity was observed. It was also found that some chemical degradation of the surface occurs at high corona currents. The extent of modification of the surface properties, as revealed by IGC, was correlated to the surface chemical composition deduced from XPS analysis as well as with the electrical conductance and the pH of the water suspensions of the cellulose fibres.

Abstract: Peroxides are important bleaching agents, industrially, for cellulosic products. They are also used in detergents. Peroxides can degrade cellulose as well as decolorize it and remove stains. Both free radicals and perhydroxyl anions have been suggested as the intermediates in the reactions occurring between cellulosic products and hydrogen peroxide. The proposed mechanisms are reviewed with emphasis primarily on cotton cellulose. Further work is required to establish unequivocally the mechanism of degradation and decolorization of cellulose products.

Abstract: Differences between values of proton rotating-frame spin relaxation time constants can be exploited to separate a solid-state13C NMR spectrum of cellulose into subspectra of crystalline and noncrystalline regions. Variations in chemical shifts and13C spin-lattice relaxation time constants can then be used to study variations in molecular order and disorder within each of the two broader categories. Mechanical damage during Wiley milling increases the content of noncrystalline cellulose and changes the nature of molecular disorder within that category. Resolution enhancement of the subspectrum assigned to crystalline cellulose reveals pairs of signals at 83.9 and 84.9 ppm (cellulose I) or 86.8 and 88.3 ppm (cellulose II) assigned to C-4 on well-ordered crystal surfaces. A broader peak in the subspectrum of crystalline cellulose I is assigned to poorly-ordered surfaces. Relative proportions in Avicel microcrystalline cellulose were estimated as: 54% in crystal interiors, 22% on well-ordered surfaces, 8% on poorly-ordered surfaces, 16% in domains of disorder extending more than a few nanometres.

Abstract: We have investigated unlignified tension wood and normally lignified wood celluloses inPopulus maximowiczii with particular reference to the composition of two crystalline phases Iα/Iβ (triclinic/ monoclinic). Four independent techniques, which enable us to detect the two phases, CP/MAS13C NMR, Fourier transform infrared microscopy, selected-area electron diffraction, and X-ray diffraction were applied. Because of the low crystallinity of wood celluloses, particularly in the case of celluloses in the lignified cell wall, no single method was decisive enough to be able to determine the composition of the two phases as one can with highly crystalline materials. The Iβ dominant structure (monoclinic crystal type) was, however, preferred for both tension and normal wood celluloses.

Abstract: Cross-linking of cotton with polycarboxylic acids, applied with catalysts based on phosphorus-containing inorganic acids, produces fabrics with excellent smooth-drying properties and which release no formaldehyde at any stage of preparation or on storage. The reaction produces cellulose ester linkages and unreacted carboxylic acid groups. Fourier transform infrared spectroscopy was used to determine the degree of esterification of polycarboxylic acids that occurred on cross-linking of cotton. The height of the carbonyl peak at 1730 cm −1 was determined on the same treated fabrics after soaking in dilute acid to convert ionized groups to free acid and then in dilute base to convert free acid to carboxylate ion. The carbonyl peak for the base rinsed fabric (ester only) was ratioed against the same peak for the acid-rinsed fabric (total carbonyl, ester plus acid) to obtain a measure of the degree of esterification. This ratio minimizes the problems of different molar extinction coefficients that are encountered when peaks from different functional groups are used.

Abstract: Edible films were prepared from methyl cellulose with various concentrations of poly(ethylene glycol) 400 (PEG400) used as a plasticizer. Water vapour and 1-octen-3-ol (an aroma compound) were selected as hydrophilic and hydrophobic volatile penetrants respectively. Their solubility and permeability through methyl cellulose-based edible films were studied using gas chromatography methods. Whatever penetrant was used, the flux increased with the PEG400 content. Transfer behaviour, i.e., the order of increased magnitude of the transfer rate, strongly depends on the nature of the volatile compound. However, water sorption only depends on the PEG400 content whereas the aroma compound sorption is affected by both the water and the PEG400 concentrations. Relationships between solubility and permeability can be partially explained by the plasticization phenomenon.

Abstract: An enzymatic treatment with cellulases fromTrichoderma viride was investigated in its effect on the pore structure of different types of bead cellulose. One objective of this study was to establish a suitable procedure for combined enzymatic treatment and solvent exchange that would restore the original pore structure which the beads had before drying without causing major losses in mechanical stability. Another aim was to further increase the accessible pore space and internal surface area for separation of large molecular weight compounds with regard to Chromatographic applications. Finally, an attempt was made to extend the findings for unsubstituted beads to the derivatives carboxymethyl (CM) and diethylaminoethyl (DEAE) cellulose beads. The enzymatically treated samples were characterized by microscopic methods and porosity measurements such as mercury porosimetry, nitrogen sorption and size exclusion chromatography. It was found that under controlled conditions the low-porosity surface layer of dried beads could be removed making the internal pore space accessible without reducing the resistance to deformation of the beads. Additionally, a shift in pore size distribution towards larger pores was observed. Supplementary swelling treatments in solvents of high swelling power could substantially restore the former porosity of the dried beads but did not enhance the accessibility to the cellulases to a considerable extent. Internal pore volume and surface area of the derivatives were dramatically increased in the case of DEAE upon enzymatic hydrolysis, however, at the expense of mechanical stability, whereas CM was found to be less affected.

Abstract: A spectroscopic study of cellulose transformation processes, such as alkali treatment and annealing, showed that, in combination with multivariate data analysis techniques, a detailed understanding of the crystalline transformation processes could be reached.13C cross-polarization magic-angle spinning (CPMAS) NMR and near-infrared (NIR) spectroscopy of cotton linters and softwood pulps analysed during the processing revealed information, after data reduction using principal components data analysis, that could be connected to structural changes of the cellulose polymorphs. The data showed that alkali treatment of cotton linters led to a cellulose conversion from cellulose I to II, while annealing, both for linters and pulps, yielded a transformation from Iα to Iα.

Abstract: Carbon-13 NMR methods were used to monitor changes in the proportions of crystalline and non-crystalline cellulose, and the exposure of chains on crystallite surfaces, in samples of alkali-treated kraft pulp and regenerated cellulose A large increase in the amount of disorderd cellulose, as a result of conversion to cellulose II, is the major effect of alkali treatment with kraft pulp Removal of small crystallites is the major effect with regenerated cellulose Samples were examined never-dried, or were vacuum-dried prior to remoistening for characterization Changes in molecular ordering consistent with pore collapse and coalescence of crystallite surfaces accompanied the removal of water

Abstract: This paper establishes the fundamental micro-mechanisms associated with the conversion of single wood pulp fibres into fibres suitable for the production of paper. It deals with an examination of the morphological and structural changes taking place in pulp fibres being subjected to cyclic mechanical actions that are representative of those experienced by fibres in mechanical refiners. Implementing the experimental procedure previously described (Hamad, 1994), qualitative answers are provided to such questions as what material property changes are associated with the various identifiable micro-mechanisms and how is the extent of damage accumulation related to wood species, pulping type, refining energy, and the number of cycles? A collation of the underlying themes responsible for material degradation indicates that a recognition of the regions of high-localized deformation and the manner in which cracks grow as well as the general weakening of the material due to structural damage and mechanical degradation of the fibre cell wall material, provide an insight into the way in which single fibres are rendered suitable for papermaking by mechanical refining.

Abstract: The surface area was determined for various papermaking woodpulps: bleached eucalyptus globulus sulphate pulp; bleached eucalyptus grandis sulphate pulp; bleached betula verrucosa sulphate pulp; bleached pine/spruce sulphate pulp; bleached pine/spruce sulphate pulp fines. The method of negative adsorption was used which gives an effective ‘wet’ surface area. By looking at negative adsorption data more closely, some inference can be made about the morphology of the substrate.

Abstract: With the aim of developing a urea biosensor, several cellulose derivatives were used to coat an all-solid-state potentiometric electrode for ammonium ion determination. In this work the physical and chemical characterization of the cellulose derivatives, as well as the changes that the activation and immobilization procedures induced in the polymers, were studied.

Abstract: The liquid Chromatographic resolution of the racemic cardiovascular drugs naftopidil and bufuralol to their corresponding enantiomers was achieved on cellulose tris-(3,5-dimethylphenyl carbamate) chiral stationary phase known as Chiralcel OD. The chiral recognition mechanism(s) involved between the chiral stationary phase and these drugs, which include hydrogen bonding, intercalative interactions, and steric interactions, among other factors, were discussed.

Abstract: The compatibility of cellulose diacetate with triacetin and esters of butylcellosolve with dicarboxylic aliphatic acids was studied for a wide range of compositions. The glass transition temperature T g ,the dielectric relaxation activation energy and the tensile creep for the plasticized systems were determined. It is shown that when the esters are added to triacetin in small amounts, which correspond to the formation of compatible systems, the plasticizing effect is enhanced and the molecular mobility of the system components is improved.

Abstract: Monomeric UO 2 2+ , CrIII, COII, NiII and CuII complexes with primary cellulose acetate (PCA) have been prepared and characterized. Infrared,1H NMR, UV/visible spectroscopy, elemental analysis, therniogravimetry, conductance and magnetic measurements were used to assign the mode of coordination in the isolated species. The investigation revealed that PCA exhibits octahedral coordination with CrIII, CoII, NiII and a square planar form with CuII whereas the UO2 moiety is virtually linear. PCA acts as a neutral bidentate chelating agent via the two oxygen atoms of the vicinal ester groups in the secondary positions forming a five-membered chelate ring. A comparative study between chelates of PCA and those previously prepared with secondary cellulose acetate (SCA) has been undertaken.

Abstract: 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.

Abstract: Maximum liquid-holding capacities of various compressed fibers in water and in a series of various organic liquids have been investigated. The maximum liquid-holding capacity versus bulk density relationships gave polynomial curves, generally with a peak. Good relative correlations for cellulose, compressed fiber pellets and wood were found for the series of liquids tested. In general, liquids that swelled wood to a low to medium range (up to 6%) did not swell appreciablyα-cellulose and sulfite pulp, while good to excellent wood-swelling agents swelled all the fibers very significantly. It was also found that the hydrogen-bonding parameter of the swelling liquid was the most important factor. The swelling rate of various compressed fiber systems in organic liquids was dramatically increased by raising the temperature. Activation energies and molar volume of the swelling liquid were linearly correlated.

Abstract: This paper gives an overview of our recent research activities on the lateral supramolecular order of a variety of native and man-made cellulosics considering respective results from the literature. Wide-angle X-ray scattering (WAXS) was the main investigation technique used. Lateral root mean squared lattice strains between 2 and 3% were determined for the materials investigated. Crystallite sizes obtained without considering lattice distortions usually do not deviate by much more than −10% from the real, i.e. fully corrected values. This means that it is sufficient to use the simple Scherrer equation for determining lateral crystallite sizes for most routine investigations of cellulosic materials. The possible superposition of WAXS peaks of the triclinic Iα and monoclinic Iβ lattice types, however, has to be considered in crystallite size determinations for Valonia cellulose. It could be shown that neglecting this fact can lead to crystallite sizes being about 20% below the true ones. Lateral crystallite dimaensions for native celluloses vary between 4nm (dissolving pulps) and 10-15 nm (Valonia). Except for bacterial cellulose, the WAXS crystallite sizes are distinctly smaller than the microfibril dimensions obtained from electron microscopy. The man-made fibres investigated showed lateral crystallite dimensions between 3 and 5nm. The importance of lateral crystallite dimensions for the properties of man-made fibres and for the alkalization process of native cellulose id demonstrated.

Abstract: Three series of oxidized celluloses – 2,3-dialdehyde celluloses (DACs), 2,3-dicarboxycelluloses (DCCs) and sodium 2,3-dicarboxycelluloses (NaDCCs) — were prepared, having incremental changes in their degrees of oxidation. Their thermogravimetric analysis (TG) and differential thermal analysis (DTA) were studied. It was found that oxidation generally destabilized cellulose at lower temperatures (below ∼ 250 °C), but at higher temperatures the oxidized products were found to be more stable. Cellulose, DACs, and DCCs all showed final weight losses in the region of 80–85%. However, 80% NaDCC and 98% NaDCC showed weight losses of only 30 and 37%, respectively.