Showing papers in "Cellulose in 2002"

Surface acetylation of bacterial cellulose

Abstract: Bacterial cellulose was partially acetylated by the fibrous acetylationmethod to modify its physical properties, while preserving the microfibrillarmorphology. The overall degree of substitution was varied from 0.04 to 2.77 bychanging the amount of acetic anhydride added. X-ray diffraction of thepartially acetylated samples showed the crystalline pattern of unmodified celluloseI up to moderate degrees of acetylation, and the change in peak widthsindicatedthat acetylation proceeded from the surface of microfibrils, leaving the coreportion unreacted. Scanning electron microscopy revealed that even low levelsofacetylation were effective to maintain the original microfibrillar morphologyofbacterial cellulose on direct drying from water.

Mercerization of primary wall cellulose and its implication for the conversion of cellulose I→cellulose II

Abstract: The mercerization of homogenized primary wall cellulose extracted fromsugar beet pulp was investigated by transmission electron microscopy (TEM),X-ray diffraction together with 13C CP-MAS NMR, and FT-IR spectroscopyFor samples resulting from acid extraction, mercerization began at 9% NaOH, whereasfor samples purified by alkaline treatment, the mercerization started at 10%NaOH The change in morphology when going from cellulose I to cellulose II wasspectacular, as all the microfibrillar cellulose morphology disappeared duringthe treatment This change in morphology was very drastic as soon as the NaOHconcentrations were increased beyond 8 and 9% for the acid and alkalinepreparedsamples, respectively On the other hand, the conversion was found to be moreprogressive in terms of increasing NaOH concentration when the transformationwas analyzed by X-ray diffraction or spectroscopy Our observations of themercerization of isolated cellulose microfibrils are consistent with theconceptof cellulose microfibrils made of parallel chains in cellulose I and crystalsofcellulose II consisting of antiparallel chains

Cellulose solutions in N-methylmorpholine-N-oxide (NMMO) – degradation processes and stabilizers

Abstract: Efficient stabilization of cellulose solutions in NMMO(1) against side reactions and their harmful effects meansprevention of both homolytic and heterolytic side reactions, which is mainlyaccomplished by trapping radicals, formaldehyde, andN-(methylene)iminium ions (5). Whileradical trapping is commonly reflected by the antioxidativeefficiency, the effectivity against heterolyticdegradationin the Lyocell dope can be expressed by the newly introduced term‘formaldehyde trapping capacity’ (FTC). Propyl gallate (PG,4), the most widely applied Lyocell stabilizer nowadays, actsas a phenolic antioxidant, and is finally oxidized to a deeply colored, highlyconjugated chromophore (11) via ellagicacid (10). It was demonstrated that 4 is alsoa quencher of formaldehyde and N-(methylene)iminium ions,both in organic solutions of NMMO and in Lyocell dope. The processes of radicaltrapping and scavenging of HCHO/5 are competitive in the caseof propyl gallate. A novel oxa-chromanol derivative, PBD (14),was designed as stabilizer for Lyocell solutions. In analogy to propyl gallate,PBD acts as a scavenger of all three dangerous species, namely HCHO,5 and radicals. Upon oxidation by radical species, PBDreleasesacetaldehyde which acts as a very efficient HCHO trap. Thus, in contrast topropyl gallate, radical trapping and HCHO trapping are not competitive. Boththeantioxidative efficiency and the capacity to trap HCHO and 5are higher for PBD as compared to propyl gallate. In preliminary stabilizertesting, mixtures of PBD and PG proved to be especially effective.

A comparative study on chemical conversion of cellulose between the batch-type and flow-type systems in supercritical water

Abstract: Microcrystalline cellulose (avicel) was treated in supercritical waterusing batch-type and flow-type systems. The flow-type system made it possibletoshorten the heating, treating and cooling times, compared with the batch-typesystem. As a result, the flow-type system was able to liquefy avicel withoutproducing any supercritical water-insoluble residue. Although hydrolyzedproducts such as glucose and fructose, and pyrolyzed products such aslevoglucosan, 5-hydroxymethyl furfural, erythrose, methylglyoxal,glycolaldehydeand dihydroxyacetone were found in common from the water-soluble portiontreatedby both systems, the flow-type system gave a water-soluble portion with morehydrolyzed and less pyrolyzed products, together with water-solubleoligosaccharides consisting of cellobiose to cellododecaose and theirdecomposedproducts at their reducing end of glucose, such as[β–glucopyranosyl]1–11 β–levoglucosan,[β–glucopyranosyl]1–11 β–erythrose and[β–glucopyranosyl]1–11 β–glycolaldehyde. Inaddition, the precipitates of polysaccharides were recovered after 12h setting of the water-soluble portion. These results indicatedthat the flow-type system can hydrolyze cellulose with minimizing pyrolyzedproducts. On the other hand, the batch-type system resulted in a higher yieldof the pyrolyzed products due to the longer treatment, but a higher yield ofglucose due possibly to the higher pressure and concomitantly higher ionicproduct of water. Based on these lines of evidence, the process to increase theyield of the sugar is discussed under supercritical water treatment.

Model films of cellulose: I. Method development and initial results

Abstract: This report presents a new method for the preparation of thin cellulosefilms. NMMO (N-methylmorpholine-N-oxide) was used to dissolve cellulose andaddition of DMSO (dimethyl sulfoxide) was used to control viscosity of thecellulose solution. A thin layer of the cellulose solution is spin-coated ontoasilicon oxide wafer and the cellulose is precipitated in deionised water. Thecellulose film is anchored onto the silicon oxide wafer by a saturated polymerlayer. Among many different polymers tested, PVAm (polyvinylamine) and G-PAM(glyoxalated-polyacrylamide) worked well. The preparation of cellulose modelfilms described in this paper resulted in films with thicknesses in the range20–270 nm and the thickness can be controlled by alteringtheconcentration of cellulose solution by addition of different amounts of DMSO.The films were cleaned in deionised water and were found to be free fromsolvents by ESCA analysis and contact angle measurements. The molecular weightdistribution of the cellulose surface material shows that there is only minorbreakdown of the cellulose chains, mainly by cleavage of the longest molecularmass fraction and without creation of low molecular mass oligomers of glucose.

The cellulose solvent system N,N-dimethylacetamide/lithium chloride revisited: the effect of water on physicochemical properties and chemical stability

Abstract: The water content in the binary systemN,N-dimethylacetamide/lithium chloride (DMAc/LiCl), acommon cellulose solvent, has been proven to be a crucial parameter. A quickdetermination of water content in DMAc based on the solvatochromism of aUV-active betain probe dye has been developed and validated. An analogousmethod, based on the solvatochromic fluorescence shift ofZelinskij's dye, which strongly depends on thesolventpolarity, was established for water determination in DMAc containing LiCl.Precise physicochemical data of the system DMAc/LiCl, such as density,viscosity, and conductivity, have been obtained. The limiting solubility forLiCl in absolute DMAc is 8.46 wt%. As shown by lightscattering experiments, water in DMAc/LiCl induces aggregation upon standingforlonger periods of time, which is even more prominent for diluted solutions andthose having a poor state of dissolution.

Cellulose synthesized by Acetobacter xylinum in the presence of plant cell wall polysaccharides

Abstract: Acetobacter xylinum was cultured in Schramm–Hestrin (SH) medium containing glucuronoxylan (xylan medium) or pectin (pectin medium). Loose bundles of cellulose microfibrils were formed in the xylan medium. In contrast the cellulose ribbons formed in the pectin medium were the same as those normally formed in SH medium.The periodic acidthiocarbohydrazidesilver proteinate method indicated that positive reacted substances located along cellulose microfibrils formed in both mediums. Freeze-fracture and deepetching electron microscopy also revealed that polysaccharides exist around cellulose microfibrils. X-ray diffractometry and Fourier Transform In-frared spectroscopy demonstrated that the addition of xylan induced a change in the ratio of cellulose Iα and Iβ. Electron diffraction analysis revealed that xylan discontinuously affected the crystalline structure of cellulose microfibrils. Pectin did not have this effect. Glucuronoxylan in the medium prevented the assembly of cellulose

Direct dyes as molecular sensors to characterize cellulose substrates

Abstract: Six dyes were selected based on their molecular structure to test theirsuitability as sensors to characterize the fine structure of cellulosesubstrates Cotton, mercerized cotton and microcrystalline cellulose werechosento represent a variety of pore structures typically encountered in practicalapplications Internally available surface areas were calculated It ispostulated that roughly 25% of the Connolly surface areas (CSA) of the sensorsDirect Blue 1, Direct Blue 14, Direct Blue 53, Direct Red 28, and Direct Red 2and 30% of the CSA of Direct Yellow 4 are representative of the space requiredfor the sensor to dock onto cellulose surfaces Molecular weight of the dyeprobes does not serve as a good indicator of sensor size Molecular structureisa critical factor to take into account when selecting a probe

Sorption of dissolved galactoglucomannans and galactomannans to bleached kraft pulp

Abstract: Sorption of mannans onto bleached kraft pulp (BKP) was investigated withreference to other interactions of mannans in mechanical pulping andpapermaking. O-Acetyl galactoglucomannans (GGM) isolated from thermomechanicalpulp (TMP), as well as enzymatically modified guar gum galactomannans (GM) wereused in the study. The results showed that deacetylation of TMP GGMs, alsooccurring during peroxide bleaching of TMP, dramatically increased thesorption.A higher sorption was also achieved after salt addition, while temperature hadno effect. Sorption of guar gum GMs onto BKP fibres was, on the other hand,quite unaffected by external conditions such as temperature, pH and saltaddition. The degree to which the pulp was beaten did not notablyinfluence the sorption either – only unbeaten pulp gave a clearly lower mannansorption. A lower number of galactose side groups, however, strongly affectedsorption – the lower the number of side groups, the higher the sorption.The molar mass did not seem to affect the rate of sorption to any higher extentat ambient temperature. At higher temperatures the rate of sorption of smallerGM polymers was, nevertheless, slightly increased. Low-molar-mass GMs alsosorbed at a higher rate onto unbeaten pulp compared to high-molar-mass mannans.GM sorption appeared to be virtually irreversible.

Synthesis and characterization of carboxymethylcelluloses (CMC) from non-wood fibers I.Accessibility of cellulose fibers and CMC synthesis

Abstract: This paper explores the production of carboxymethylcellulose (CMC) fromseveral bleached cellulose pulps obtained from non-wood species. The chemicalcomposition (α-cellulose, hemicellulose and lignin content), the degreeofswelling, viscosity, solubility in concentrated NaOH and crystallinity ofsoda/AQ cellulose pulps from abaca, jute, sisal, linen and Miscanthussinensis were determined. The pulps were carboxymethylated by one andtwo successive reaction steps in aqueous medium under identical conditions. Thedegree of substitution (DS) of CMC was found to be dependent upon the source ofthe cellulose pulp, but generally it was close to 1 with one etherificationtreatment and around 2 after the second. The molar mass of CMC was found to bedependent on the initial intrinsic viscosity of the cellulose pulp. The weightaverage molar mass of our CMCs ranged from 1.5 × 105 to2.8 × 105. Increasing the DS up to 2 improved the CMC solubility, butviscosity slightly decreased due to a slight degradation of the polymer.

Surface fluorination of paper in CF4-RF plasma environments

Abstract: Plasma-based technologies are an exciting alternative for cellulose andpaper modification. Barrier coatings and surface functionalization of celluloseenhances properties and creates new possibilities for cellulose-based products.A parallel plate radio frequency (RF)-plasma reactor was used to modify papersubstrates under discharge parameters such as power, time and pressure. Carbontetrafluoride RF-plasma treatment of paper caused intense fluorination and itwas demonstrated that the fluorination reaction mechanisms can be controlled bythe external plasma parameters. Fluorine contents as high as 51.3% (contactangle=147°) were obtained for the treated cellulose. It was shown that eventreatment times as low as 30 s can generate relative surface fluorineatomic concentrations as high as 30%. High resolution ESCA and ATR-FTIRanalysisindicated covalently bound CFx functional groups with CF4treatment. It was found that under certain experimental conditionssuper-hydrophobic paper surfaces are created by combining the high surfacefluorine atomic concentrations with specific plasma-generated surfacetopographies.

Effect of cellulase-assisted refining on the properties of dried and never-dried eucalyptus pulp

Abstract: The effect of two different cellulases on the hornification phenomenon,in which drainability (Schopper–Riegler method) and mechanical propertiesdiminish when pulps are dried, was studied The enzyme applications testedincluded a commercial enzyme named ComC (Pergalase A40 from CIBA) and alaboratory enzyme from Paenibacillus sp strain BP-23namedCelB Industrial never-dried Eucalyptus globulus bleachedkraft pulp was split in two halves and one of them was dried at ambientcontrolled conditions We compared enzyme effects on both pulps (wet pulp anddried pulp) before and after PFI mill refining Enzyme applications increaseddrainability (Schopper–Riegler method) and water retention value (WRV) ofnever-dried bleached pulp, although this did not imply an enhancement of themechanical properties of paper Cellulase treatment of dried pulps, bycontrast,gave rise to increased drainability and WRV and also to improved mechanicalproperties The changes caused by drying became less significant after enzymeapplication Handsheets from CelB-treated dried pulps showed an improvement oftensile and burst indexes while tear decreased The effect produced by CelB canbe considered a biorefining step In fact, by means of enzyme treatment withCelB the properties of paper manufactured from dried pulp equalled theproperties attained from wet fibres, with the exception of tear index Changeswere also found in surface fibre morphology, such as flakes and peeling due tocellulase treatment The surface modification of fibres with cellulases givesrise to better bonding properties and a closer structure of paper The finalconclusion is that treatment with cellulases could compensate the hornificationeffect and lead to an important saving of refining energy The novel enzyme,CelB, was the most effective in improving paper properties and counterbalancingthe hornification effect caused by drying

Changes of cellulose fiber wall structure during drying investigated using NMR self-diffusion and relaxation experiments

Abstract: The self-diffusion of water sorbed in cellulose fibers was investigatedby means of NMR during slow drying in order to follow changes in the celluloseporous structure. In pulp fibers pores with at least one dimension on theμm scale were observed at high amounts of sorbed water and nm-scale pores atlow amounts. Beating affected the μm-scale pores. Regenerated cellulosefibers had nm-scale pores up to high amounts of water. Bulk water was observedas a second component with long T 2 in a CPMGexperiment. The sequence of water removal for kraft pulp fibers is: (1) bulkwater, (2) water in μm-scale pores and (3) water in nm-scale pores.

CP/MAS 13C NMR and electron diffraction study of bacterial cellulose structure affected by cell wall polysaccharides

Abstract: Acetobacter xylinum was cultured in Schramm–Hestrin medium containing pectin (pectin medium), xylan (xylan medium), or glucomannan (mannan medium). X-ray diffractometry revealed that xylan and glucomannan affected the size of the cellulose crystals and their d-spacing values. Solid-state cross polarization magic angle spinning carbon-13 nuclear magnetic resonance spectroscopy indicated that the ratio of cellulose Iα was reduced by the addition of polysaccharides. These effects were more remarkable on the cellulose in the mannan medium than that in the xylan medium, and were scarcely observed in the pectin medium. Electron diffraction analysis revealed that these effects on hemicelluloses along cellulose microfibrils are continuous in the mannan medium and discontinuous in the xylan medium. These findings suggest that the uronic acid in the polysaccharides prevents interactions with cellulose leading to alterations of the structure of the cellulose crystal.

Characterization of cellulose by SEC-MALLS

Abstract: Norway spruce (Picea abies) cellulose samplesdissolved in lithium chloride/N,N-dimethyl-acetamide(LiCl/DMAc) covering a wide range of average molecular weights were analyzed bysize exclusion chromatography (SEC) and multi-angle laser light detection(MALLS). The molecular weight distribution of the samples was compared to themolecular weight distribution of cotton linters cellulose samples. To obtaincomplete dissolution of high-molecular-weight wood cellulose, previouslypublished procedures for dissolving cellulose in LiCl/DMAc were modified. SECseparation was performed using macroporous monodisperse polymer particles ascolumn matrix. The refractive index increment (dn/dc)μ forcellulose in 0.5% LiCl/DMAc was found to be 0.104. The radius of gyration,RG, of cellulose in 0.5% LiCl/DMAc depended on the molecular weight,M, according to the relation RG ∝ M0.55. Celluloseprepared from sprucewood by the sulfite cooking process had a broad molecularweight distribution compared to cotton linters cellulose.

Cellulose derivatives from cellulosic material isolated from Agave lechuguilla and fourcroydes

Abstract: Fibers isolated from Agave lechuguilla(lechuguilla) and fourcroydes (henequen) contain about 80%cellulose, 5% hemicellulose and 15% lignin. They are a renewable resource,interesting as feedstock for new products obtained by chemicalfunctionalization. In the present paper the reactivity of such fibrousmaterialsunder typical conditions for modification of cellulose was studied. Treatmentwith n-octanol/aqueous NaOH of the fibers leads to an activated expandedgel-like material with enhanced accessibility. Carboxymethylation, sulfation,acetylation and tritylation reactions as well as subsequent carboxymethylationof the trityl derivative and selective oxidation of the primary hydroxylfunction of carboxymethylated products with TEMPO/NaBr/NaClO were successfullycarried out under conditions typical for cellulose reactions. The products werecharacterized by means of 13C-NMR and 1H-NMR spectroscopyandHPLC after complete depolymerization, by GPC, and by the determination ofsolubility.

Miscibility of cellulose acetate with vinyl polymers

Abstract: Binary blend films of cellulose acetate (CA) with flexible syntheticpolymers including poly(vinyl acetate) (PVAc), poly(N-vinyl pyrrolidone) (PVP),and poly(N-vinyl pyrrolidone-co-vinyl acetate) [P(VP-co-VAc)] were preparedfrommixed polymer solutions by solvent evaporation. Thermal analysis by DSC showedthat CA of any degree of substitution (DS) was not miscible with PVAc, but CAwith DS less than 2.8 was miscible with PVP to form homogeneous blends. Thestate of mixing in CA/P(VP-co-VAc) blends was affected not only by the DS of CAbut also by the VP/VAc copolymer composition. As far as CAs of DS<2.8 andP(VP-co-VAc)s with VP contents more than ca. 25 mol% were used,theCA/copolymer blends mostly showed a miscible behaviour irrespective of themixing ratio. FT-IR measurements for the miscible blends of CA/PVP andCA/P(VP-co-VAc) revealed the presence of hydrogen-bonding interactions betweenresidual hydroxyls of CA and carbonyls of N-vinyl pyrrolidone units, which maybe assumed to largely contribute to the good miscibility.

Recombinant cellulose crosslinking protein: a novel paper-modification biomaterial

Abstract: Cellulose-binding domains have been isolated from various cellulases, and proteins, which lack hydrolytic activity. The hypothesis that a cellulose-binding domain can be used to alter surface and mechanical properties of paper was tested. Two cellulose-binding domains from Clostriium cellulovorans were fused to form a cellulose crosslinking protein (CCP). The recombinant bifunctional cellulose-binding protein was expressed in E. coli, appliedby immersion onto Whatman cellulose filter paper, and its mechanical properties were tested. The purified protein improved the treated paper's mechanical properties (tensile strength, brittleness, Young's modulus and energy to break). In addition, cellulose crosslinking protein treatment was shown to transform filter paper into a more water-repellent paper. The binding of cellulose-binding domains to cellulose under a wide range of envi-ronmentalconditions, without the need for chemical reactions, and its biodegradability make them attractive moieties for the design of a new class of paper-modification materials.p>

Characterization of different types of cellulose by dielectric spectroscopy

Abstract: Various ‘well dried’ solid celluloses, such as nativecelluloses from different sources, different pulps and regenerated cellulosefibers were compared by dielectric relaxation spectroscopy (DRS) in the lowfrequency (10 mHz to 5 MHz) and low temperature(−130 to 20 °C) range. No significant differences werefound in the polymeric dynamics. In addition, the influence of the watercontenton the β-relaxation and the βwet relaxation wasinvestigated for morphologically very different celluloses such as cottonlinters, highly amorphous bead cellulose and lyocell fibers. The lyocell fiberswere investigated in the unmodified form and after modification by a treatmentwith alkali, after mild bleaching and after chemical crosslinking. It was foundthat the water content influences the dielectric dynamics and the intensityparameters differently for these different materials. NaOH-activation usingdifferent lye concentrations also influenced the dielectric dynamics. Finally,opportunities and limitations of DRS as a diagnostic tool are discussed.

Synthesis and characterization of carboxymethylcelluloses from non-wood pulps II. Rheological behavior of CMC in aqueous solution

Abstract: This paper concerns the rheological behavior of carboxymethylcelulloses(CMC) derived after one and two successive steps from different non-woodbleached cellulose pulps. CMC rheological characterization was achieved in0.1M NaCl solution, as a function of polymer concentration. Theevidence of a critical concentration (C* < 1 g/L) is discussedfromsteady shear and dynamic experiments. Rheological properties of the CMC werefound to depend on the cellulose source reactivity and on their degree ofsubstitution (DS). Higher molecular weight of initial cellulose was accompaniedby higher apparent intrinsic viscosity of the CMC produced. Depending on theCMCconcentration and on the degree of etherification, the system behaves as asolution or as a gel. In the case of abaca CMC sample, it is shown that afteronly one step of chemical modification and above a polymer concentration of20 g/L, the system behaves as a gel. The gel behavior was studied asafunction of temperature. In the temperature range from 25 to 45°C, the rheological behavior was found to remain almostconstant due to the existence of dispersed swollen aggregates. This unusualcharacteristic represents an advantage for applications such as oil recovery inthe petroleum industry, where viscosity of the recovered fluid should not diminishwith temperature.

Biodegradation of β-1,4-linked polyglucuronic acid (cellouronic acid)

Abstract: Biodegradability of β-1,4-linked polyglucuronic acid (cellouronicacid), which was prepared from regenerated cellulose by2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation underaqueous conditions, was examined by enzymatic treatments and incubationtreatments with microorganisms collected from some soil samples. Degradation ofcellouronic acid was traced by size exclusion chromatography (HPSEC) or totalorganic carbon (TOC) of the treated products or solutions, respectively.Cellouronic acid was depolymerized by a commercial crude cellulase anddecreasedin its weight average degree of polymerization from about 1600 to 40 by thecellulase treatment at 20 °C for 40 days. 13C-NMRanalysis and liquid chromatography of the treated products showed thathydrolysis-type enzymes present in the crude cellulase as contaminantsprimarilydepolymerized cellouronic acid to give glucuronic acid. When aqueous solutionscontaining cellouronic acid were incubated with soil microorganisms for morethan 3 days, the TOC values decreased to less than 20% of the initial value,depending on molecular weight of the cellouronic acid used. The decreasing rateof TOC for cellouronic acid was clearly higher than that ofcarboxymethylcellulose, which is one of the cellulose derivatives havingcarboxymethyl substituents. These results imply that cellouronic acid has bothbiodegradability and metabolizability in the natural environment.

Effect of a nonionic surfactant on Trichoderma cellulase treatments of regenerated cellulose and cotton yarns

Abstract: It has been shown that some surfactants affect the hydrolysis of cellulose by cellulase In this study, the effect of the surfactant Tween 20 on the hydrolysis of different cellulosic fibers was investigated and related to the cellulose fiber structure It was found that this non-ionic surfactant enhanced the enzymatic saccharification of highly crystalline cellulosics such as Avicel, Tencel and cotton but not of cuprammonium rayon The enhanced saccha-rification effected by the surfactant is attributed to inhibition of non-productive sorption of the endoglucanase of the cellulose surface which gives greater access to the cellulose chain ends by the exoglucanase Although all three fibers lost tensile strength as a result of the enzymatic treatment, no further decrease was effected by the presence of the surfactant

TEM study of band-like cellulose assemblies produced by Acetobacter xylinum at 4 °C

Abstract: Two kinds of band-like cellulose assemblies, coarse and densestructures, are produced in Hestrin–Schramm medium at 4 °Cusing smooth colonies isolated from Acetobacter xylinumATCC23769, whereas ribbon cellulose assemblies are produced by the samecoloniesat 28 °C. The dense and the coarse band-like assembliesconsist of many strand-like cellulose entities (‘strands’) and areextruded perpendicularly to the long axis of the bacterial cell. In an earlystage of incubation at 4 °C, the dense band-like assembly isproduced and the number of strands decreases gradually with increasingincubation time at 4 °C, probably because the number of activeTC subunits decreases as a result of the low-temperature shock for thebacteria.In contrast, the coarse band-like assembly is clearly observed after about 1h of incubation at 4 °C. The number of strands inthe coarse band-like assembly is about one third of that of the dense band-likeassembly and does not change during the incubation time of about 6h. In the selected-area electron diffraction (ED) experiment, thedense band-like assembly gives crystalline reflections corresponding to thecellulose II type crystal, while the coarse band-like assembly does not giveanycrystalline reflections under the same ED conditions.

Reactivity of dissolving pulp: characterisation using chemical properties, NMR spectroscopy and multivariate data analysis

Abstract: The reactivity of dissolving pulp was experimentally determined in termsof residual cellulose in viscose. The correlations between 11 chemicalproperties of pulp and filter values and residual cellulose contents of viscosewere then investigated by multivariate data analysis. Both the viscose filtervalue and the residual cellulose were well modelled from the 11 propertiesby partial least squares regression. The results show that pulps with highacetone extractable fractions, high magnesium contents, low alkali resistanceand low viscosity, gave low viscose filter values and low residual cellulosecontents. Pulps with low residual cellulose contents also had low carboxylgroupcontents and low polydispersity. The results are interpreted as that in pulpwith high reactivity, the hemicellulose content is low and that the cellulosechains are shorter and more soluble in alkali. An explanation of the positiveeffect from the high extractive content is that the extractives facilitate thediffusion of carbon disulfide. A principal component analysis of CP/MAS13C-NMR spectral data of six pulp samples showed that differences inreactivity between the pulps could be explained by variations in the hydrogenbonds in the cellulose and/or changes in the glucosidic bonds. In a separatestudy electron beam processing enhanced the reactivity, i.e. lowered theresidual cellulose content, of the investigated pulps. The magnitude of theelectron dose, within the tested range (5.4–23.7 kGy), didnotseem to be important, but the reactivity within pulp sheets tended to be ratherinhomogeneous.

Surface properties of CTMP fibers modified with xylans

Abstract: This study investigated the effect of modification with xylan on the surface properties of chemithermomechanical pulp (CTMP) from spruce. The surface modifications were carried out by controlled sorption of birch xylan from solution at high temperature and high pH. Several different analysis techniques were used to study the effects on fiber surface composition and morphology. The ESCA technique showed a reduction in the amount of carbons not bound to oxygen in the C(1s) resolved peak after treatment. Variations in surface topography between untreated samples and samples with xylan were studied with SEM and AFM in the tapping mode. Scanning electron micrographs show micrometersized xylan particle structures spread over the fiber surfaces. AFM images reveal differences in the fine structure of fibers. The modified fibers exhibit a nanometersized, bumplike morphology not seen on the untreated fibers. The wetting properties of single fibers were determined with the Wilhelmy plate technique and the water sorption of CTMP paper sheets was studied using a dynamic contactangle tester. The surface modification of CTMP with xylan significantly decreased the advancing contact angle of single fibers and also improved the water sorption of sheets.

Preparation of cellulose and cellulose derivative azo compounds

Abstract: Wood pulp and cotton linter are the most common sources of cellulose forindustrial use. Methyl cellulose (MC) and cellulose sulfate (CS) were preparedusing bleached wood pulp and cotton linter. Coloured azo compounds were alsoprepared from coupling cellulose, wood pulp, MC and CS with aromatic diazoniumsalt. The presence of electron-releasing or withdrawing substituents affectedthe electrophilic substitution reaction. The produced azo compounds werecharacterized by FT-IR methodology, as well as mass spectrometry, in which thefunctional groups and the ion fragments of the products were analyzed.

The use of amidoximated cellulose for the removalof metal ions and dyes from waste waters

Abstract: The adsorption of metal ions such as Cu(II), Cr(III), Cd(II) and Ni(II)and dyes such as Acid Blue 25, Calmagite and Eriochrome Blue Black Bis performed onto amidoximated cellulose (Am-Cell). Different ways are possible for theadsorption of these pollutants onto Am-Cell : adsorption of each pollutantaloneon the support, or cumulative adsorption of both metal ions and dyes on the samesupport. In the last case, the pollutants may be adsorbed simultaneously from aunique solution, or successively from two different solutions, whatever theorder. Am-Cell loaded or not with metal ions shows a high capacity for dyeadsorption. Ternary complexes involving metal/dye/amidoxime are formed. Theobserved stoichiometries are 1/1/1 with Cu(II), Cr(III) and Cd(II) ions and1/1/2with Ni(II) ion. A quasi-total and specific desorption of either metal ions (bytreatment with ethylenediaminetetracetic salt) or of dyes (by heating inaqueoussolution) is possible from these ternary complexes. Concerning the dyes, manysuccessive adsorption/desorption cycles are possible without a noticeablechange in the adsorption capacity.

Synthesis of novel adamantoyl cellulose using differently activated carboxylic acid derivatives

Abstract: New adamantane carboxylic acid esters of cellulose (adamantoylcelluloses) were synthesized homogeneously inN,N-dimethylacetamide/LiCl using differently activatedcarboxylic acid derivatives. This includes the reaction of cellulose with1-adamantoyl chloride and with adamantane-1-carboxylic acid after insitu activation with p-toluenesulfonyl chlorideand with 1,1′-carbonyldiimidazole, which is a new and efficient tool. Thedegree of substitution (DS) has been determined by means of 1H NMRspectroscopy using the perpropionylated adamantoyl cellulose samples. DS valuesas high as 2.1 were achieved. The reaction efficiency was 85% and the DS can becontrolled by the molar ratio and the reaction conditions applied. The reactionoccurs faster at the primary position compared to the secondary ones. Theproducts are soluble in various organic solvents dependent on the DS.Preliminary results of subsequent modifications and properties of theadamantoylcelluloses are discussed as well.

Effect of Mannanase and Lipase on the properties of colloidal wood extractives and their interaction with mechanical pulp fines

Abstract: The effects of enzymatic treatments of dissolved and colloidalsubstances (DCS) released from thermomechanical pulp (TMP) have beeninvestigated. A model dispersion of DCS was made by leaching several portionsofTMP in distilled water and separating the fibrous material. Some samples wereenriched in colloidal particles by removing dissolved substances usingultra-filtration. The DCS, which had been subjected to different enzymatictreatments, were added in a fixed quantity to TMP fines that had been madecationic, and were subsequently used to form handsheets. All DCS additionsincreased the content of lipophilic extractives in the sheets. Lipase gave acomplete hydrolysation of triglycerides into free fatty acids. The untreatedDCSgave no significant decrease in tensile strength, because of the relativelysmall addition. A treatment of the DCS with Lipase gave a higher extractivescontent and a tensile strength on the same level as the reference. A Mannanasetreatment gave a decrease in strength compared with the reference at the sameamount of extractives in the sheet. A combined treatment with Mannanase andLipase gave a more pronounced decrease in tensile strength. Two possiblereasonsfor the differences in strength at a given amount of extractives weresuggested:(i) the destabilisation of the colloidal wood extractivesdue to the Mannanase could affect the distribution of the colloid in the sheet,making it more detrimental to sheet strength compared with the stable colloid.This would account for the observation that Lipase did not affect sheetstrengthas such, but the combination with Mannanase gave the lowest tensilestrength; (ii) the decomposition of galactoglucomannans in aqueoussolution would diminish their positive effect on tensile strength and/or affectthe adsorption of the colloid. A reflectometry technique was used to quantifythe adsorption of the differently treated DCS onto a model surface of thecationic fines. Colloidal wood extractives were identified on the surfacesafteradsorption using staining and light microscopy. No variations in adsorbedamounts were found that could explain the differences in sheet strength, whichindirectly suggests that the distribution of the colloid over the surface wasaffecting the ability of a strong bonded joint to be formed between two suchsurfaces.

Probing the surface polarity of native celluloses using genuine solvatochromic dyes

Abstract: The surface polarity of native celluloses has been investigated by the following solvatochromic dyes: dicyano-bis (1,10)-phenanthroline iron (II) Fe(phen)2 (CN)2 (1), bis(4-N,N-dimethylamino)-benzophenone (2), and cou-marine 153 (3). Linear Solvation Energy (LSE) relationships and the UV/Vis data have been used to characterize the surface polarity of different native cellulose batches in terms of the empirical Kamlet–Taft polarity parameters α (hydrogen bond acidity), β (hydrogen bond basicity), and π * (dipolarity/polarizability). α, β, π *and calculated Reichardt's E T (30) values are reported for various native and regenerated cellulose samples with different degrees of crystallinity. The degree of crystallinity of the cellulose samples has been determined by X-ray. The microcrystalline environment of cellulose can be exactly parameterized in terms of the α, β and π *values. It shows a fairly strong acidity α and a low dipolarity/polarizability. For the amorphous sections smaller α and larger π * values are observed. The correspondence of the empirical polarity parameters determined has been discussed in relation to results from pyrene fluorescence and zetapotential measurements.