Mercerized Cellulose Research Articles

Rapid synthesis of graft copolymers from natural cellulose fibers

Cellulose is the most abundant natural polysaccharide polymer, which is used as such or its derivatives in a number of advanced applications, such as in paper, packaging, biosorption, and biomedical. In present communication, in an effort to develop a proficient way to rapidly synthesize poly(methyl acrylate)-graft-cellulose (PMA-g-cellulose) copolymers, rapid graft copolymerization synthesis was carried out under microwave conditions using ferrous ammonium sulfate–potassium per sulfate (FAS–KPS) as redox initiator. Different reaction parameters such as microwave radiation power, ratio of monomer, solvent and initiator concentrations were optimized to get the highest percentage of grafting. Grafting percentage was found to increase with increase in microwave power up to 70%, and maximum 36.73% grafting was obtained after optimization of all parameters. Fourier transforms infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA/DTA/DTG) analysis were used to confirm the graft copolymerization of poly(methyl acrylate) (PMA) onto the mercerized cellulose. The grafted cellulosic polymers were subsequently subjected to the evaluation of different physico-chemical properties in order to access their application in everyday life, in a direction toward green environment. The grafted copolymers demonstrated increased chemical resistance, and higher thermal stability.

Influence of cellulose polymorphs on the polypropylene crystallization

Results of the hitherto research work on alkalisation of lignocellulosic materials have been much divergent. In view of the above, the subject of this study is mercerization of cellulose from pine wood. This choice of the subject permitted observation of transformation of cellulose I to cellulose II with no participation of other components of lignocellulosic materials. According to X-ray results, during mercerization the isolated cellulose was easily (completely) transformed into cellulose II variety, while the pine wood was converted more slowly to cellulose II polymorphs. Therefore, it could be concluded that the presence of lignin and hemicelluloses in wood prevented the transformation from cellulose I to II. The main objective of this research was to establish the effect of cellulose varieties on the nucleation ability of different fillers by using differential scanning calorimetry (DSC) and polarizing microscopy. The nucleating effect of the fillers occurs only in the presence of cellulose I variety. In contrast, the presence of cellulose II variety seems to practically eliminate the nucleating effect of the fillers. Moreover, nucleation of the mercerized wood (mixture of cellulose I and II) can be also observed, but this effect is not strong. It should be emphasised that as yet no correlation has been reported between the quantitative composition of cellulose polymorphic forms (appearing not only in wood, but in cellulose isolated from wood as well) and the nucleation ability of lignocellulosic fillers.

Regioselective cationization of cellulosic materials using an efficient solvent-minimizing spray-technique

Cationization of different cellulosic materials was successfully accomplished using an efficient solvent-minimizing spray-technique. The obtained materials were studied and evaluated in regard to reaction efficiency and regioselectivity using 1D and 1H–13C correlated 2D NMR experiments. The high consistencies and temperatures applied using the spray-technique resulted in reagent effective etherifications and shorter reaction times. The NMR spectra indicated that the spray-technique favors substitutions at position O-6, showing a regioselectivity of O-6 > O-2 > O-3 for softwood kraft pulp (SKP) and cotton linters. However, cationization of mercerized cellulose and dissolving pulp, using the spray-technique, demonstrated more efficient reactions compared to SKP and cotton, and a regioselectivity of O-6 ≥ O-2 > O-3. Nanocrystalline cellulose showed the lowest reactivity and a regioselectivity of O-6 ≫ O-2 > O-3. In this work we provide information on structure–property relationships and characterization methods for modified polysaccharides, together with a solvent system that is well known industrially and in line with sustainability aspects.

Improved Graft Copolymerization of Some Modified Cellulose Polymers with Vinyl Monomers Using Dibenzoyl Peroxide (DBPO) as Initiator

An improved efficient method for grafting of mercerized cellulose with acrylonitrile, acylamide, 4-vinylpyridine and styrene monomers using dibenzoyl peroxide (DBPO) as an initiator was studied. The results show that the order of the reactivity of the monomers is styrene > 4- vinyl pyridine > acrylonitrile >acrylamide. Under optimal conditions, the extent of graft copolymerization of styrene onto cellulose has shown a substantial increasing trend. The percentages of grafting yield (G.Y.%), grafting efficiency (G.E.%), IR spectra, and X-ray diffraction were measured. The I t was shown that X-ray diffraction spectra of grafted cellulose increases one more peak than that of pure cellulose with a noticeable decrease in crystallinity.

Crystal transition from cellulose II hydrate to cellulose II

Samples of cellulose II hydrate were prepared by immersion of mercerized cellulose II in anhydrous hydrazine followed by washing with water. The synchrotron X-ray fiber diffraction and solid-state 13C NMR measurements showed that cellulose II hydrate had a larger unit cell that contained water molecules with lower degree of crystallinity than mercerized cellulose II, but it had basically the same molecular conformation as mercerized cellulose II. The crystal transition from cellulose II hydrate to cellulose II was monitored using synchrotron X-ray diffraction under controlled relative humidity. In the drying process, the cellulose II hydrate gradually contracted, and this decreased the distance between the hydrophobic stacking sheets of molecular chains, while maintaining its sheet structure. The absence of an obvious transition point and the irreversibility of the transition indicated a random location of the water molecules occurred in the unit cell of cellulose II hydrate. On annealing a sample in hot water, the cellulose II hydrate was converted to cellulose II. Cellulose II hydrate was unstable at high temperatures, even in water.

A physical organic chemistry approach to dissolution of cellulose: effects of cellulose mercerization on its properties and on the kinetics of its decrystallization

The effects of alkali treatment on the structural characteristics of cotton linters and sisal cellulose samples have been studied. Mercerization results in a decrease in the indices of crystallinity and the degrees of polymerization, and an increase in the α-cellulose contents of the samples. The relevance of the structural properties of cellulose to its dissolution is probed by studying the kinetics of cellulose decrystallization, prior to its solubilization in LiCl/N,N-dimethylacetamide (DMAc). Our data show that the decrystallization rate constants and activation parameters are only slightly dependent on the physico-chemical properties of the starting celluloses. This multi- step reaction is accompanied by a small enthalpy and large, negative, entropy of activation. These results are analyzed in terms of the interactions within the biopolymer chains during decrystallization, as well as those between the two ions of the electrolyte and both DMAc and cellulose.

Thermal decomposition of mercerized linter cellulose and its acetates obtained from a homogeneous reaction

Cellulose acetates with different degrees of substitution (DS, from 0.6 to 1.9) were prepared from previously mercerized linter cellulose, in a homogeneous medium, using N,N-dimethylacetamide/lithium chloride as a solvent system. The influence of different degrees of substitution on the properties of cellulose acetates was investigated using thermogravimetric analyses (TGA). Quantitative methods were applied to the thermogravimetric curves in order to determine the apparent activation energy (Ea) related to the thermal decomposition of untreated and mercerized celluloses and cellulose acetates. Ea values were calculated using Broido's method and considering dynamic conditions. Ea values of 158 and 187 kJ mol-1 were obtained for untreated and mercerized cellulose, respectively. A previous study showed that C6OH is the most reactive site for acetylation, probably due to the steric hindrance of C2 and C3. The C6OH takes part in the first step of cellulose decomposition, leading to the formation of levoglucosan and, when it is changed to C6OCOCH3, the results indicate that the mechanism of thermal decomposition changes to one with a lower Ea. A linear correlation between Ea and the DS of the acetates prepared in the present work was identified.

Some aspects of acetylation of untreated and mercerized sisal cellulose

We report here on some aspects of the acetylation in LiCl/N,N-dimethylacetamide, DMAc, of untreated and mercerized sisal cellulose, hereafter designated as sisal and M-sisal, respectively. Fiber mercerization by NaOH solution has resulted in the following changes: 29.9% decrease in the index of crystallinity; 16.2% decrease in the degree of polymerization and 9.3% increase in α-cellulose content. A light scattering study of solutions of sisal, M-sisal, microcrystalline and cotton celluloses in LiCl/DMAc has shown that they are present as aggregates, with (an apparent) average aggregation numbers of 5.2, 3.2, 9.8, and 35.3, respectively. The presence of these aggregates affects the accessibility of cellulose during its functionalization. A study of the evolution of the degree of substitution, DS, of cellulose acetate as a function of reaction time showed an increase up to 5 h, followed by a decrease at 7 h. Possible reasons for this decrease are discussed. As expected, M-sisal gave a higher DS that its untreated counterpart.

Water dispersion of cellulose II nanocrystals prepared by TEMPO-mediated oxidation of mercerized cellulose at pH 4.8

Mercerized wood cellulose was oxidized by 4-acetamide-TEMPO/NaClO/NaClO2 system at 60 °C and pH 4.8 for 1–5 days. Mostly individual nanocrystals 4–7 nm in width and 100–200 nm in length were obtained by ultrasonication of the oxidized product in water. The nanocrystals had the cellulose II structure, and carboxylate contents of 2.0–2.4 mmol/g, indicating that these carboxylate groups were selectively formed on the cellulose II crystallite surfaces in mercerized cellulose. Moreover, the original wood cellulose and mercerized cellulose were acid-hydrolyzed, and then subjected to the TEMPO-mediated oxidation under the same conditions at pH 4.8 to prepare reference samples. TEM images, light transmittance and rheological properties of water dispersions showed that the nanocrystals prepared from mercerized cellulose by the TEMPO oxidation and sonication in water had the highest dispersibility of individual nanocrystals with less amounts of bundles in water, resulting from the highest carboxylate contents.

Removal of Ca(II) and Mg(II) from aqueous single metal solutions by mercerized cellulose and mercerized sugarcane bagasse grafted with EDTA dianhydride (EDTAD)

In a previous work, chemically modified cellulose (EMC) and sugarcane bagasse (EMMB) were prepared from mercerized cellulose (MC) and twice-mercerized sugarcane bagasse (MMB) using ethylenediaminetetraacetic dianhydride (EDTAD) as modifying agent. In this work we described in detail the modification of these materials in function of reaction time and EDTAD amount in the reaction media. The resistance of ester bond at pH 1, 2, 11, and 12 was also evaluated by FTIR. The results were used to model the hydrolysis process and a kinetic model was proposed. The modified materials (EMMB and EMC) were used to adsorb Ca 2+ and Mg 2+ ions from aqueous single solutions. The adsorption isotherms were developed at two pH values. These materials showed maximum adsorption capacities for Ca 2+ and Mg 2+ ions ranging from 15.6 to 54.1 mg/g and 13.5 to 42.6 mg/g, respectively. The modified material from sugarcane bagasse (EMMB) showed larger maximum adsorption capacities than modified material from cellulose (EMC) for both metals.

Cellulose mercerization: Use of amino acid‐glycerol ethers as wetting agents

AbstractThe action of a new nonconventional series of (tryptophan‐phenylalanine‐histidine and tyrosine)‐glycerol‐ether surfactants as wetting agents in hot cotton mercerization was studied. The mercerization result was evaluated with the barium hydroxide absorption number, water absorbency and moisture regain, and mechanical properties of fibers; the dyeability of the mercerized samples with a direct and reactive dye was also studied. An improvement was observed for all the above parameters in the presence of the aforementioned wetting agents despite their being used in very low concentrations. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Adsorption of chromium (VI) ion from aqueous solution by succinylated mercerized cellulose functionalized with quaternary ammonium groups

Succinylated mercerized cellulose (cell 1) was used to synthesize an anion exchange resin. Cell 1, containing carboxylic acid groups was reacted with triethylenetetramine to introduce amine functionality to this material to obtain cell 2. Cell 2 was reacted with methyl-iodide to quaternize the amine groups from this material to obtain cell 3. Cells 2 and 3 were characterized by mass percent gain, degree of amination and quaternization, FTIR and CHN. Cells 2 and 3 showed degrees of amination and quaternization of 2.8 and 0.9 mmol/g and nitrogen content of 6.07% and 2.13%, respectively. Cell 3 was used for Cr (VI) adsorption studies. Adsorption equilibrium time and optimum pH for Cr (VI) adsorption were found to be 300 min and 3.1, respectively. The Langmuir isotherm was used to model adsorption equilibrium data. The adsorption capacity of cell 3 was found to be 0.829 mmol/g. Kinetic studies showed that the rate of adsorption of Cr (VI) on cell 3 obeyed a pseudo-second-order kinetic model.

Adsorption of Cu(II), Cd(II), and Pb(II) from aqueous single metal solutions by mercerized cellulose and mercerized sugarcane bagasse chemically modified with EDTA dianhydride (EDTAD)

This work describes the preparation of new chelating materials derived from cellulose and sugarcane bagasse for adsorption of Cu 2+, Cd 2+, and Pb 2+ ions from aqueous solutions. The first part involved the mercerization treatment of cellulose and sugarcane bagasse with NaOH 5 mol/L. Non- and mercerized cellulose and sugarcane bagasse were then reacted with ethylenediaminetetraacetic dianhydride (EDTAD) in order to prepare different chelating materials. These materials were characterized by mass percent gain, X-ray diffraction, FTIR, and elemental analysis. The second part consisted of evaluating the adsorption capacity of these modified materials for Cu 2+, Cd 2+, and Pb 2+ ions from aqueous single metal solutions, whose concentration was determined by atomic absorption spectroscopy. These materials showed maximum adsorption capacities for Cu 2+, Cd 2+, and Pb 2+ ions ranging from 38.8 to 92.6 mg/g, 87.7 to 149.0 mg/g, and 192.0 to 333.0 mg/g, respectively. The modified mercerized materials showed larger maximum adsorption capacities than modified non-mercerized materials.

Adsorption of Cu(II), Cd(II), and Pb(II) from aqueous single metal solutions by succinylated mercerized cellulose modified with triethylenetetramine

This study describes the preparation of two new chelating materials derived from succinylated mercerized cellulose (cell 1). Cell 1 was activated through two different methods by using diisopropylcarbodiimide and acetic anhydride (to form an internal anhydride) and reacted with triethylenetetramine in order to obtain cell 2 and 4. New modified celluloses were characterized by mass percent gain, concentration of amine functions, elemental analysis, and infrared spectroscopy. Cell 2 and 4 showed degrees of amination of 2.8 and 2.3 mmol/g and nitrogen content of 6.07% and 4.61%, respectively. The capacity of cell 2 and 4 to adsorb Cu 2+, Cd 2+, and Pb 2+ ions from single aqueous solutions were examined. The effect of contact time, pH, and initial concentration of metal ions on the metal ions uptake was also investigated. Adsorption isotherms were well fitted by the Langmuir model. The maximum adsorption capacity of cell 2 and 4 were found to be 56.8 and 69.4 mg/g for Cu 2+; 68.0 and 87.0 mg/g for Cd 2+; and 147.1 and 192.3 mg/g for Pb 2+, respectively.

The conversion from cellulose I to cellulose II in NaOH mercerization performed in alcohol–water systems: An X-ray powder diffraction study

The slurry-mercerization (SM) processes in 2-propanol–water and 2-propanol–ethanol–water and wet-mass-mercerization (WMM) process in ethanol–water solvents are investigated. Based on X-ray diffraction measurements in the earlier reports, we have derived a mathematical method to evaluate more exactly the conversion of cellulose I (CI) to cellulose II (CII) and used it to survey the effects of different alkali treatments on cellulose crystals. This method is very useful when the crystal system changes in a certain set of experiments are compared with each other. The optimal alcohol concentration in SM processes was found to be 80–92 w/w-% in 2-propanol–water solution, 85–90 w/w-% in 2-propanol–ethanol–water solution and 45–55 w/w-% in the WMM process. In the WMM mercerization, the effect of the solvent/cellulose ratio showed that the conversion to CII increased linearly with a decreasing solvent/cellulose ratio. Temperature increase, as well as higher lye concentration, had a positive effect on the conversion of CI to CII. This study confirms also our earlier results that the concentration of soluble lye in the used solvent system is the most important factors in the mercerization of cellulose.

Characterization of Aggregate Structure in Mercerized Cellulose/LiCl·DMAc Solution Using Light Scattering and Rheological Measurements

The structure of a semidilute solution of mercerized cellulose (CC1m) in 8% (w/w) LiCl.DMAc, which contained some aggregates, was investigated using static and dynamic light scattering measurements. The static scattering function of the polymer solution containing a small amount of aggregates can be separated into fast- and slow-mode components by combining static and dynamic light scattering measurements. The osmotic modulus was identical for the fast-mode component of the CC1m solutions and the native cellulose (CC1) solutions, in which cellulose is dispersed molecularly. This indicates that the molecularly dispersed component of the CC1m solutions has an identical conformation with the cellulose molecules in the CC1 solutions. The correlation length was also identical for the fast-mode components of CC1m solutions and the CC1 solutions, indicating that these solutions have the same mesh size of the polymer entanglement. These observations for the fast-mode components are consistent with the concentration dependence of the zero shear rate viscosity and the plateau modulus estimated in the rheological measurements. The slow-mode component, on the other hand, gave information on the aggregate structure in the CC1m solution. The radius of gyration of the aggregate structure estimated from the slow-mode component was about 70 nm, which is independent of the concentration of the solution. The plots for particle scattering factor of the slow-mode component lay between the theoretical curve of a sphere and a Gaussian chain, implying that the structure of the aggregate in the CC1m solution is like a multiarm polymer. A characteristic time of the slow-mode component calculated with the translational diffusion coefficient and the radius of gyration were almost identical with the relaxation time of the long-time relaxation observed in the rheological measurements. This indicates that the long-time relaxation of CC1m solutions originates in the translational diffusion of the aggregate structure in the solution.

Synchrotron X-ray structures of cellulose Iβ and regenerated cellulose II at ambient temperature and 100 K

Synchrotron X-ray data have been collected to 1.4 A resolution at the NE-CAT beam-line at the Advanced Photon Source from fibers of cellulose Iβ and regenerated cellulose II (Fortisan) at ambient temperature and at 100 K in order to understand the effects of low temperature on cellulose more thoroughly. Crystal structures have been determined at each temperature. The unit cell of regenerated cellulose II contracted, with decreasing temperature, by 0.25%, 0.22% and 0.1% along the a, b, and c axes, respectively, whereas that of cellulose Iβ contracted only in the direction of the a axis, by 0.9%. The value of 4.6×10−5 K−1 for the thermal expansion coefficient of cellulose Iβ in the a axis direction can be explained by simple harmonic molecular oscillations and the lack of hydrogen-bonding in this direction. The molecular conformations of each allomorph are essential unchanged by cooling to 100 K. The room temperature crystal structure of regenerated cellulose II is essentially identical to the crystal structure of mercerized cellulose II.

Carboxymethylation of cellulose in the new solvent dimethyl sulfoxide/tetrabutylammonium fluoride

The new cellulose solvent dimethyl sulfoxide (DMSO)/tetrabutylammonium fluoride (TBAF) was applied as reaction medium for the carboxymethylation of mercerized cellulose from sisal and cotton linters. The reaction parameters studied were the molar ratio of reagent and NaOH to anhydroglucose unit (AGU) and the addition of the NaOH either as an aqueous solution or as solid particles. Size Exclusion Chromatography results (SEC) indicated that the dissolution medium and/or derivatizing method used in the present work causes a certain depolymerization on the cellulose chains The pattern of substitution within the AGU and along the polymer chains of the carboxymethylcellulose (CMC), which was analyzed by 1H NMR spectroscopy and HPLC after acidic depolymerization of the CMC, is in the order O-6>O-2≥O-3. With regard to the mole fractions of the different repeating units, samples prepared using aqueous NaOH possess a statistic content, while by using solid NaOH a deviation from statistically calculated values was observed. As a consequence of the non-statistics, the solubility in water of these samples starts at a DS 0.85, while conventionally prepared CMC are water-soluble at a DS as low as 0.4.

Second Harmonic Generation Measurements for Biomacromolecules: Celluloses

The molecular chain orientation of mercerized cellulose II was examined by optical second harmonic generation (SHG) measurements. The SHG intensities of several kinds of mercerized cellulose II were found to be much larger than those expected for a structural model with an antiparallel molecular chain orientation as proposed by X-ray studies. This result suggests that the orientation of mercerized cellulose II is parallel as suggested by molecular dynamics simulation. © 2004 The Optical Society of Japan

Synthesis and characterization of oxidized cellulose

AbstractSamples of oxidized cellulose (OC) with various carboxyl contents and degrees of crystallinity were obtained by the oxidation of native and mercerized cellulose with a solution of nitrogen(IV) oxide in CCl4. A detailed characterization of these OC samples was performed. The effect of oxidation conditions (concentration of N2O4 in the solution and oxidation time) and starting cellulose material on OC characteristics (carboxyl, carbonyl and nitrogen content, degree of crystallinity and polymerization, surface area and swelling, and acidic properties) was investigated. Reactivity in the oxidation process was higher in mercerized cellulose than in native cellulose. The action of dilute solutions (10–15%) of N2O4 did not affect the degree of crystallinity of cellulose samples. Under these conditions, the oxidation took place mainly in amorphous regions and on the surface of crystallites. Oxidation in a concentrated (40%) N2O4 solution led to the destruction of crystallites, which increased the surface area and swelling of cellulose in water. The surface area and the swelling of OC samples increased with a decrease in the index of crystallinity. The acidic properties of OC were shown to increase with an increase of swelling in water. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4785–4791, 2004