共查询到20条相似文献,搜索用时 31 毫秒
1.
Anders Thygesen Jette Oddershede Hans Lilholt Anne Belinda Thomsen Kenny Ståhl 《Cellulose (London, England)》2005,12(6):563-576
A comparative study of cellulose crystallinity based on the sample crystallinity and the cellulose content in plant fibres
was performed for samples of different origin. Strong acid hydrolysis was found superior to agricultural fibre analysis and
comprehensive plant fibre analysis for a consistent determination of the cellulose content. Crystallinity determinations were
based on X-ray powder diffraction methods using side-loaded samples in reflection (Bragg-Brentano) mode. Rietveld refinements
based on the recently published crystal structure of cellulose Iβ followed by integration of the crystalline and amorphous
(background) parts were performed. This was shown to be straightforward to use and in many ways advantageous to traditional
crystallinity determinations using the Segal or the Ruland–Vonk methods. The determined cellulose crystallinities were 90–100 g/100 g
cellulose in plant-based fibres and 60–70 g/100 g cellulose in wood based fibres. These findings are significant in relation
to strong fibre composites and bio-ethanol production. 相似文献
2.
Marija Gorjanc Katja Jazbec Martin Šala Rok Zaplotnik Alenka Vesel Miran Mozetič 《Cellulose (London, England)》2014,21(4):3007-3021
Weakly ionised gaseous plasma created in a moist tetrafluoromethane gas at a low pressure with an electrodeless radiofrequency discharge was applied to modify the surface properties of cellulose fibres. The plasma was used to increase the adsorption of zinc oxide (ZnO) nanoparticles such that cellulose fibres with good ultraviolet (UV) protective properties could be created. The UV protection factor (UPF) values of the ZnO-functionalised fibres were determined as a function of the plasma treatment time. The chemical and physical surface properties of the plasma-treated fibres were examined using scanning electron microscopy, X-ray photoelectron spectroscopy, and wettability tests. The quantity of zinc on the fibres was determined using inductively coupled plasma mass spectroscopy. The results indicated that 30 s of plasma treatment resulted in ZnO-functionalised samples with lower UPF values than samples without plasma treatment due to the creation of fluorine-rich functional groups on cellulose fibres and the agglomeration of ZnO nanoparticles. The highest UPF values (50+) were obtained when samples were treated with plasma for 10 s. These high UPF values were a result of the increased adsorption of uniformly distributed ZnO nanoparticles caused by fibres surface functionalization and roughening upon plasma treatment. Furthermore, the mechanical properties of textiles treated with moist CF4 plasma for 10 s were slightly improved. 相似文献
3.
A. Legras A. Kondor M. Alcock M. T. Heitzmann R. W. Truss 《Cellulose (London, England)》2017,24(11):4691-4700
Inverse Gas Chromatography (IGC) is a gas sorption technique to determine the surface energy of natural fibres. The surface energy is directly related to the thermodynamic work of adhesion and it reflects the fibre adsorption capacity and its wettability. However, natural fibres have a complex surface chemistry of numerous organic species and present physical asperities that render the surface energetically heterogeneous. Since IGC is typically performed at infinite dilution where only the higher energetic sites interact with the solvent, a single measure of surface energy is likely to be misleading as the surface energy changes with changing chemical composition. Here we present the dispersive and acid-base surface energy profiles of flax and kenaf fibres as well as continuous filament fibres produced by a dry jet, wet spinning process (cellulose B). We injected a series of n-alkanes at finite dilution to obtain the dispersive energy distribution profile at \(30\,^{\circ }\hbox {C}\) and 0% RH. The acid-base contributions were determined by injection of mono polar probes (dichloromethane, ethylacetate) at the same surface coverages and applying the Van Oss method. The cellulose B fibres were the most energetically homogeneous, while the bast fibres were shown to have a higher polar component and much broader surface energy distributions than the cellulose fibres. 相似文献
4.
P. H. F. Pereira H. J. C. Voorwald M. O. H. Cioffi M. L. C. P. Da Silva A. M. B. Rego A. M. Ferraria Maria Norberta De Pinho 《Cellulose (London, England)》2014,21(1):641-652
Cellulose fibres obtained from sugarcane bagasse were submitted to a purification process, which consisted of an acid hydrolysis for elimination of the major part of lignin and hemicellulose. This was followed by a delignification process carried out in two steps to yield crude cellulose (CCell) fibres in the first one and with a subsequent bleaching in order to yield bleached cellulose fibres (BCell). Composites of crude and bleached cellulose fibres with hydrous niobium phosphate, cell/NbOPO4·nH2O, were subsequently synthesized. Scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction characterization of the obtained materials showed CCell/NbOPO4·nH2O and BCell/NbOPO4·nH2O are real composites. The nature of the cellulose (CCell or BCell) has an important role on the composites obtained, namely on the niobium salt composition at the composite surface. The synthesis of membranes of both cellulose and mixed matrix cellulose/NbOPO4·nH2O was only possible when the bleached cellulose was used. 相似文献
5.
Summary Microanalytical investigations have been made on samples of ceramic fibres (SiC fibres, (Nicalon) C fibre coated with TiN) and fibre-reinforced ceramics (SiC- and glass-matrices). High resolution Auger electron spectroscopy (HRAES), electron probe microanalysis (EPMA) and scanning electron microscopy were employed for these examinations. Analysis was best performed with HRAES on account of its lateral and depth resolution. Some of the problems involved in this technique are discussed e.g. electron beam effects. AES depth profiles of ceramic fibres are reported and compared with the surface analysis of fibres in the composites after being broken in situ.
Mikroanalytische Untersuchungen faserverstärkter keramischer Werkstoffe相似文献
6.
The aim of this work is to study the influence of low-pressure plasma treatment on cellulose fibres to improve the adhesion between a polymeric matrix and natural fibres used as reinforcement. To evaluate fibre wettability, contact angle measurements were carried out on flax fibres after treatment with plasma under several conditions. Similarly, contact angle measurements were performed without plasma treatment. A comparison between all the samples led to the definition of the optimal plasma treatment conditions. Once the latter were determined, composite materials were prepared with treated and untreated flax fibres and a low-density polyethylene matrix. Composites, with different fibre contents (5 and 40%) and different fibre lengths (1 and 10 mm), were manufactured using a mixer and a hot plate press. The tensile strengths of the composites were assessed to determine optimal fibre content and length, and the plasma treatment effect was also quantified. It was found that the higher the fibre content, the higher the tensile strength, and the higher the Young’s modulus; however, fibre length did not affect tensile strength. Regarding plasma treatment, composites with treated fibres exhibited a considerably improved tensile strength and Young’s modulus. Plasma treatment effects were also studied by X-ray photoelectron spectroscopy and by differential scanning calorimetric. Finally, an analysis of the fibre surface and an interaction study between the matrix and the fibres was conducted with scanning electron microscopy. 相似文献
7.
Heidrun Pionteck Werner Berger Bernd Morgenstern Dietrich Fengel 《Cellulose (London, England)》1996,3(1):127-139
The influence of different solvents on the morphology of cellulose during the dissolution process was studied. Spruce sulfite pulp, cotton linters and hydrolysed cotton linters were treated for a short time with lithium chloride: N,N-dimethylacetamide (LiCl:DMAc) and an alkaline solution of iron sodium tartrate (EWNN), respectively. The changes occurring at the fibre surfaces and within the cell walls were observed by scanning as well as by transmission electron microscopy. The cellulose fibres show significant differences in the dissolution behaviour when comparing the reaction of the two solvents. Using LiCl:DMAc, the cotton linters fibres become lamellar separated and within the spruce sulfite pulp fibres solvent channels appear in the first step with the fibrils becoming separated. In contrast, EWNN has a swelling effect on the surface of the cellulose fibres. Both solvent systems predominantly affect the ends of the fibres and places where the wall structure has been damaged. 相似文献
8.
Lignin adsorption on cellulose fibre surfaces: Effect on surface chemistry, surface morphology and paper strength 总被引:2,自引:0,他引:2
Natalia Maximova Monika Österberg Krista Koljonen Per Stenius 《Cellulose (London, England)》2001,8(2):113-125
The adsorption of lignin on cellulose fibres at neutral pH and the effects of calcium ions and a cationic polyelectrolyte (PDADMAC) on the adsorption have been studied. The surface coverage by lignin was determined by electron spectroscopy for chemical analysis (ESCA). The morphology of the lignin layer was studied by atomic force microscopy (AFM). The effect of adsorbed polyelectrolyte and lignin on the strength properties of the paper was also studied. The adsorbed amount of lignin increased monotonically with lignin concentration. Addition of calcium ions resulted in a very high surface coverage by lignin. PDADMAC did not enhance the adsorption of lignin, but without addition of polyelectrolyte the lignin was very weakly attached to the fibre surface. PDADMAC formed complexes with lignin in solution. At high polymer/lignin concentration ratios the charge of the complex was positive and it adsorbed irreversibly as large blobs. At low ratios the complex was easily washed away from the fibre surface. When PDADMAC was pre-adsorbed on the fibre surface the lignin adsorbed as small granules at all lignin concentrations. Neither PDADMAC nor lignin alone increased the strength of pulp sheets significantly. However, together they increased the bonding between fibres. 相似文献
9.
Alfredo Calvimontes Peter Mauersberger Mirko Nitschke Victoria Dutschk Frank Simon 《Cellulose (London, England)》2011,18(3):803-809
These studies aimed to investigate in detail changes on cellulose surfaces treated with low pressure oxygen plasma at various
exposure times. Modifications of cellulose films were studied in respect to topography effects by means of atomic force microscopy
and scanning electron microscopy. Chemical effects of plasma treatment were studied using X-ray photoelectron spectroscopy
and X-ray diffractometry. Results show that the topographical evolution of the surfaces to rougher ones is not at all gradual.
Local maxima of fractionation and the surface size regularity were investigated using surface fractal analysis and Wenzel
roughness factors, respectively. It was shown, that plasma treatments decompose the cellulose material by formation of highly
functionalized molecules. Such plasma-initiated and supported reactions taking place on the sample surface. The bulk phase
and in particular, the crystalline domains are not influenced by plasma treatments. The studies provide useful information
to understand the plasma reaction on amorphous and crystalline regions of cellulose surfaces and allow to predict effects
of the plasma treatment on physical and chemical properties of much more complex cellulose systems such as cotton fibres and
fabrics. 相似文献
10.
Tobias Köhnke Carla Pujolras Johannes P. Roubroeks Paul Gatenholm 《Cellulose (London, England)》2008,15(4):537-546
This study investigates the adsorption of (glucurono)arabinoxylan (GAX) on cellulose fibres and the properties thereof. A
water-soluble GAX, from barley husks (Hordeum vulgare), was isolated using chlorite delignification and alkaline extraction followed by enzymatic purification. The isolated GAX
fraction showed an arabinose to xylose ratio of 0.22 and a weight average molar mass of 20,200 g/mol, as determined by size
exclusion chromatography (SEC) in DMSO:H2O. The GAX was adsorbed on cellulose fibres under well controlled conditions, where temperature and initial concentration
of GAX proved to be important parameters in controlling the level of adsorption. The adsorption process was also dependent
on xylan molecular structure. Carbohydrate analysis on the modified fibres showed a preferential adsorption of low substituted
xylans (arabinose to xylose ratio of ∼0.10). During the adsorption process the GAX solution was analyzed using SEC-RI-MALLS
in aqueous solvent, which demonstrated a molecular xylan adsorption on cellulose fibres. Additionally, a decrease in light
scattering responses, which corresponds to an adsorption of aggregated xylan and/or xylan with a great tendency towards self-association,
could be observed during the adsorption process. This was demonstrated by adsorption of GAX on regenerated cellulose fibres
(Lyocell), which compared to native fibres possesses a relatively smooth fibre surface. Atomic force microscopy analysis visualised
a heterogeneous decoration of the Lyocell fibres with xylan agglomerates. The effect of GAX adsorption on paper strength was
also investigated. A GAX modified kraft pulp showed an evident increase in tensile strength, which might be due to a retained
fibre–fibre bonding ability for xylan coated fibrils after drying and rewetting. 相似文献
11.
Ramesh-Babu Adusumali Moritz Reifferscheid Hedda Weber Thomas Roeder Herbert Sixta Wolfgang Gindl 《Macromolecular Symposia》2006,244(1):119-125
Summary: A broad variety of regenerated cellulose fibres was subjected to single fibre tensile tests in order to determine the modulus of elasticity, tensile strength, and failure strain. The results were compared to glass fibres and flax fibres, which are considered the most important technical and natural fibres, respectively. With regard to their modulus of elasticity and tensile strength, regenerated cellulose fibres showed clearly lower values than glass fibres, even when their low density was taken into account. The average modulus of elasticity and tensile strength of regenerated cellulose fibres was also lower than the values measured for flax fibres, but when variability was considered, both fibres performed similarly. In terms of interfacial shear strength with polypropylene, lyocell fibres performed significantly less well than sized glass fibre and ramie fibre. The most important difference between regenerated cellulose fibres and both glass and flax fibres is their high failure strain and thus high work to fracture. The high work to fracture of regenerated cellulose fibres makes them particularly useful for composite applications where high fracture toughness is required. 相似文献
12.
One of the most important treatments performed on cellulosic fibres to improve properties such as dimensional stability, tensile strength and lustre, is mercerisation. The aim of this work was to study the crystallinity, accessibility and unit cell structure changes occurring in three types of regenerated cellulose fibres (lyocell, modal and viscose) that were mercerised with caustic soda solutions of different concentrations. Differences were observed between the behaviour of the viscose type fibres (viscose and modal) and that of the lyocell fibres. For the viscose type fibres, the proportion of crystalline regions increased at low alkali concentrations, while for lyocell fibres a decrease in crystallinity was observed. In all three fibres there was a transformation from cellulose II to amorphous cellulose. While for lyocell the transformation was partial, the modal and in particular the viscose fibres showed a complete transformation, and the swelling agent caused the fibre to dissolve at high caustic concentrations. 相似文献
13.
In the present study the effect of chemically and mechanically treated cellulose materials on the degree of polypropylene transcrystallisation was investigated. The cellulose materials which were sulphite fibres, microcrystalline cellulose (MCC) and knife milled sulphite fibre, were either chemically treated by esterification or mechanically treated by beating. The esterified cellulose materials did not induce a transcrystalline layer, however, all unesterified cellulose materials clearly induced a transcrystalline layer. The fibres which were mechanically treated by beating gave a higher degree of transcrystallisation than the untreated ones. Our results show the importance of the surface chemistry of the added fibres on the growth of transcrystallisation in polypropylene composite materials. 相似文献
14.
JOSE-ANTONIO TREJO-O'REILLY JEAN-YVES CAVAILLE ALESSANDRO GANDINI 《Cellulose (London, England)》1997,4(4):305-320
The surface modification of various cellulosic materials was studied in heterogeneous conditions using different grafting
agents bearing anhydride or isocyanate reactive groups. Some of these reagents were oligomeric, others polymeric and most
were chosen so as to provide a non-polar character to the surface of the fibres in view of their possible use as reinforcing
agents in composites based on polymeric matrices. The success of these chemical modifications was assessed by Fourier-transform
Infrared Spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and elemental analysis. The accessibility
of the superficial OH groups varied as a function of the coupling agent in terms of both molecular size and chemical nature
and ranged between 1 and 3% of the total hydroxy groups borne by the initial cellulose sample.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
15.
Kavkler K Demšar A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(2):740-746
The investigation and characterisation of historical objects can be an exacting piece of work because of the small quantity of material that can be investigated and the degradation of the material and its value, which sometimes demands only non-destructive methods. In this study, as one such method, Raman spectroscopy was used to investigate the cellulose fibres of painting canvases and linings. Historical samples of fabrics were taken from different paintings and their linings from different locations in Slovenia. Raman spectra were recorded on the fibres of these historical samples. Additionally, a database of the Raman spectra of modern cellulose fibres was created and compared with the literature data. Differences in the Raman spectra of different cellulose fibres were observed, and on this basis fibres of different types were discriminated. The recorded Raman spectra of historical samples were compared with the database spectra of modern cellulose fibres. Strong luminescence effects because of the changes caused by ageing, degradation products and surface contamination caused difficulties in interpreting the Raman spectra of historical fibres. The luminescence effects were partly overcome by prolonged exposition times and previous "signal quenching" with the laser. The Raman spectra of historical cotton showed no luminescence effects, and only slight differences to the reference spectra of modern cotton fibres appeared, whereas the Raman spectra of historical flax fibres were overwhelmed with luminescence and showed changes in spectra through degradation. The research showed that by using Raman spectroscopy the identification and differentiation of different cellulose fibres and materials that accompany cellulose in the fibres are possible and that degraded and aged material can be differentiated. 相似文献
16.
Ola Sundman 《Cellulose (London, England)》2014,21(1):115-124
The adsorption of four commercial non-ionic cellulose derivatives onto two different model surfaces of cellulose fibres has been studied with surface plasmon reflectance. The model surfaces of cellulose were ultrathin films of either nano fibrillated cellulose or regenerated cellulose on Au(s). Partial least squares models were used in the analysis of the data and it was found that the type of cellulose model surface seems to be most important for both the total adsorption and the initial adsorption rate of the studied cellulose derivatives. It is believed that this can be explained by morphological differences between the surfaces, and it was found that the properties of the cellulose derivatives that affect the adsorption of the two types of cellulose surface differ. For adsorption onto a NFC-based model surface, the type of cellulose derivative and the polydispersity index (PDI) of the cellulose derivative seem to be the two most important variables for the observed adsorption of these cellulose derivatives. For the regenerated cellulose surface the three most important variables are the M n of the cellulose derivatives, the DS NMR of the methyl celluloses, and PDI of the cellulose derivatives. Thus the adsorption of cellulose derivatives on the NFC-based cellulose model surface is strongly affected by the type of substituent, while the same cannot be said for a surface regenerated from N-methylmorpholine-N-oxide. Additionally, the DS NMR of methyl celluloses affects their adsorption differently on the investigated cellulose model surfaces. 相似文献
17.
Boufi S Rei Vilar M Parra V Ferraria AM Botelho do Rego AM 《Langmuir : the ACS journal of surfaces and colloids》2008,24(14):7309-7315
Ultrathin films of cellulose were functionalized with iron protoporphyrin IX (FePP). Spin-coating allows the production of silylated cellulose films in a controlled way. Cellulose regeneration is achieved through the hydrolyzation of the silane groups, exposing the film to acidic vapors. To enhance the reactivity of the cellulose surface to the protoporphyrin, carbonyldiimidazole (CDI) was used as an activator. The effect of different spacers on the porphyrin grafting such as 1,8-diaminooctane and 1,4-phenylenediamine was studied. The highest level of cellulose functionalization with FePP was achieved when both the cellulose film and FePP were activated by CDI and a diaminoalkane was used as a spacer between the surface and the FePP. ATR/MIR (attenuated total reflection in multiple internal reflections) was performed in situ to follow the kinetics of the different chemical reactions with the cellulose surface. ATR/MIR proved again to be a powerful tool for probing the surface reaction. X-ray photoelectron spectroscopy permitted the elemental analysis of the cellulose surface after the chemical modification. 相似文献
18.
Uttam C. Paul Avinash P. Manian Barbora Široká Heinz Duelli Thomas Bechtold 《Cellulose (London, England)》2013,20(5):2481-2490
Multivalent ions take a significant role in the sorption of soluble polysaccharides on solid cellulose substrates and thus demonstrate an important principle in structural polysaccharide organisation. Sorption of Fe(III)–alginate complexes on lyocell fibres as model for the insoluble cellulose matrix has been studied between pH 3–13, at 30 and 60 °C. Sorption maximum of the Fe(III)–alginate complex was observed at pH 3 where the sorbed amounts of alginate and iron were 6,600 and 85 mg iron per kg cellulose respectively. Under the experimental conditions used, a concentration of 0.05 mM Fe(III) is sufficient to achieve surface sorption of Fe(III)–alginate complex. The alginate sorption exhibited minor dependence on molar ratio of Fe(III) to alginate. In environmental scanning electron microscopy no deposition of Fe-hydroxides on the fiber surface was detected. The thickness of the adsorbed Fe(III)–alginate layer on the fiber surface was estimated with 12–22 nm. Tensile strength and abrasion resistance of Fe(III)–alginate treated fibers were not reduced through the sorption treatment. Alginate modified cellulose is of interest as material for medical application, as sorbent and textile finish. 相似文献
19.
20.
The microstructure and thermal properties of lyocell and other regenerated cellulose fibres (viscose and modal) were analysed using DSC, TG and FTIR. The FTIR spectral analysis showed that lyocell is the most crystalline fibre and is composed principally of crystalline cellulose II and amorphous cellulose. Likewise, the thermal analysis showed that lyocell has a higher thermal stability than viscose and modal fibres, as the difference between the onset temperature for its decomposition process was as high as 20 °C. 相似文献