Molecular Weight Of Carboxymethyl Cellulose Research Articles

The Effect of Molecular Weight of Carboxymethyl Cellulose on the Dispersion of Silicon Suspensions Investigated by the Ultrasonic Degradation Method

The Effect of Molecular Weight of Carboxymethyl Cellulose on the Dispersion of Silicon Suspensions Investigated by the Ultrasonic Degradation Method

Controllable Synthesis of Carboxymethyl Cellulose and Its Application in Tobacco Sheets

Carboxymethyl cellulose (CMC) with different degree of substitution (DS) was prepared by controlling feed ratio and times of alkalization and etherification. CMC with different molecular weight was prepared by degradation of hydrochloric acid solution. Orthogonal experiments were designed to study the effects of addition amount, molecular weight and DS of CMC on the tensile strength of tobacco sheets. The effects of CMC on the thermal properties and aerosol release of tobacco sheets were also studied. The results showed that the addition amount and the molecular weight of CMC had obvious effect on the tensile strength of tobacco sheets. The DS of CMC had no significant effect on the tensile strength of tobacco sheets. The addition of CMC improved the thermal stability of tobacco sheets to a certain extent, and had certain influence on the content of nicotine in aerosol.

Effect of the Molecular Weight of Carboxymethyl Cellulose on the Flotation of Chlorite.

The present study aimed to investigate the influence mechanism of carboxymethyl cellulose (CMC) on the flotation of fine chlorite. To this end, a series of flotation tests, sedimentation tests, and microscope analyses were conducted. Flotation tests revealed an inverse relationship between particle size and the recovery of chlorite, indicating that finer particles exhibited higher recovery rates. Moreover, it was observed that the recovery of fine chlorite was significantly associated with the water recovery (proportion of water entering the floated product to the weight of water in the initial flotation suspension) and a variety of frother types. Based on these findings, it can be inferred that froth entrainment may constitute a crucial component of the recovery mechanism underlying fine chlorite. Thus, reducing froth entrainment (the phenomenon of hydrophilic minerals entering floated products through foam water) is the key to depress chlorite flotation. Flotation tests indicate that fine chlorite recovered into froth products can be depressed effectively by CMC with a high molecular weight. The results of sedimentation tests and microscope analyses in the presence of CMC prove that CMC with a high molecular weight generates flocculation on fine chlorite particles while that with a low molecular weight does not. It is suggested that the depression of chlorite flotation may be attributed to the reduction in the entrainment resulting from the flocculation induced by CMC.

Effect of Physicochemical Properties of Carboxymethyl Cellulose on Diffusion of Glucose.

Soluble dietary fibers (SDF) are known to reduce the post-prandial plasma glucose levels. However, the detailed mechanisms of this reduced glucose release in the human gut still remain unclear. The aim of our study was to systematically investigate the effect of different types of SDF on glucose release in an in vitro model as a prerequisite for the selection of fibers suitable for application in humans. Three types of carboxymethyl cellulose (CMC) were used to investigate the correlations between fiber concentration, molecular weight (MW), and viscosity on diffusion of glucose using a side-by-side system. CMC solutions below the coil overlap (c*) influenced the glucose diffusivity only marginally, whereas at concentrations above c* the diffusion of glucose was significantly decreased. Solutions of lower MW exhibited a lower viscosity with lower glucose diffusion compared to solutions with higher MW CMC, attributed to the higher density of the solutions. All CMC solutions showed a systematic positive deviation from Stokes-Einstein behavior indicating a greater rise in viscosity than reduction in diffusion. Therefore, our results pave the way for a new approach for assessing glucose diffusion in solutions comprising dietary fibers and may contribute to further elucidating the mechanisms of post-prandial plasma glucose level reduction.

Applicability of Modified Cox-Merz Rule to Concentrated Suspensions

The present work studied the rheological properties of concentrated non-colloidal aqueous suspensions of graphite particles together with carboxymethyl cellulose (CMC) having various molecular weights, especially focusing on the applicability of the modified Cox-Merz rule. These suspensions were investigated as model slurries to produce anode electrodes of lithium ion batteries. In the case of suspensions containing high molecular weight CMC, the complex viscosity resulting from the measurements of frequency dependence of the viscoelastic moduli at high strain values was in good agreement with the steady state viscosity. That is, the data conformed to the modified Cox-Merz rule. However, the data obtained from suspensions containing low molecular weight CMC did not agree with the modified Cox-Merz rule. The difference in the applicability of this model is considered to be attributed to variations in the ability of the suspensions to recover to a stable state during the application of cyclic strain.

Understanding the Role of Polymeric Binders in Water Based Lithium Ion Electrodes

Polymers find application in Lithium ion Batteries (LiB) as binders, providing cohesion in the dry electrode layer as well as adhesion to the current collector. They may also be added as a thickener to control the flow and hence the processing behavior of the paste. Furthermore, polymeric binders can act as dispersing agents for active material or carbon black particles, thus strongly determining the component distribution in dry electrodes. Despite the vast amount of research activities in the field of LiB, the contribution of the binder to the cell performance still remains elusive. Therefore, the adsorption of carboxymethylcellulose (CMC) on LiFePO4 and graphite particles as active material was investigated. The flow behavior of the electrode pastes as well as the electrical conductivity, mechanical properties and microstructure of corresponding dry electrodes were thoroughly characterized. Rheological measurements were carried out to study paste flow behavior as a function of CMC and solid particle concentration. The electrical conductivity of thin electrode layers was measured using the four point resistivity test. The adhesion force between electrode layer and current collector was determined via 90°-peel test. Thick electrode layers were prepared to investigate the cohesion in the electrode employing compression, bending and shear tests. Finally, the microstructure of the dry electrodes was characterize by means of scanning electron microscopy (SEM). Yield stress and viscosity exhibit a pronounced minimum with increasing CMC concentration for both the cathode and anode pastes, indicating that CMC acts as dispersing agent at low concentrations and as a thickener at higher concentration when the equilibrium adsorption concentration is exceeded. Furthermore, the degree of substitution of CMC have no significant influence on the slurry viscosity, whereas higher molecular weights and CMC concentrations lead to significantly higher viscosities. Electrical conductivity of thin electrode layers increases with increasing CMC concentration and yields a pronounced maximum when the equilibrium adsorption concentration is covered, suggesting a critical polymer concentration at which electrode components ideally distribute. In addition, mechanical tests show no clear dependence of the adhesion strength on CMC concentration, irrespective of the degree of substitution or molecular weight, i.e. it does not contribute to the adhesive strength. In contrast, the cohesive strength of the electrode layers increases with higher polymer concentration and molecular weight, but decreases with increasing degree of substitution. Micrographs of the electrode layers show an alignment of the particles for electrodes based on high molecular weight CMC. Preliminary measurements exhibit higher adhesion strength when adding styrene butadiene rubber (SBR), whereas cohesion strength and electrical conductivity significantly decreases. This demonstrates that the optimum CMC concentration has to be chosen according to the required specifications with respect to cohesion and electrical performance.

Sterilization effects on the handling and degradation properties of calcium phosphate cements containing poly (D,L -lactic-co-glycolic acid) porogens and carboxymethyl cellulose.

Injectable, self-setting calcium phosphate cements (CPCs) are synthetic bone substitutes considered favorable for the repair and regeneration of bone due to their osteocompatibility and unique handling properties. However, their clinical applicability can be compromised due to insufficient cohesion upon injection into the body coupled with poor degradation rates that restricts new bone formation. Consequently, carboxymethyl cellulose (CMC) was incorporated into CPC formulations to improve their cohesion and injectability while poly (D,L -lactic-co-glycolic acid) (PLGA) porogens were added to introduce macroporosity and improve their biodegradation rate. Like most biomaterials, CPCs are gamma irradiated before clinical use to ensure sufficient sterilization. However, it is well known that gamma irradiation also reduces the molecular weight of CMC and PLGA via chain scission, which affects their material properties. Therefore, the aim of this study is to measure the effect that gamma irradiation has on the molecular weight of CMC at varying doses of 15, 40, or 80 kGy and investigate how this affects the handling (i.e., injectability, cohesion, washout, and setting times) and in vitro degradation behavior of CPC formulations. Results reveal that the molecular weight of CMC decreases with increasing gamma irradiation dose, thereby reducing the viscosifying capabilities of CMC, which causes CPCs to deteriorate more readily. Further, the addition of CMC seems to inhibit the degree of phase transformation during cement setting while the subsequent reduction in molecular weight of PLGA after gamma irradiation improves the in vitro degradation rate of CPCs due to the faster degradation rate of low molecular weight PLGA. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2216-2228, 2019.

Synthesis and grafting of carboxymethyl cellulose from environmental pollutant cellulosic wastes of textile industry

Purpose This study aims to explore the use of knitted rag by synthesizing different grades of carboxymethyl cellulose (CMC) by applying multiple-step carboxymethylation techniques. Design/methodology/approach CMC was synthesized from knitted rag, a cellulosic waste of textile and garment industries, in aqueous ethanolic sodium hydroxide and subsequently mono-chloroacetic acid reaction medium. Low-substituted to high-substituted products were obtained from single-step to seven-step carboxymethylation of cellulose. In this way, it was possible to produce low-cost and different grades of substituted carboxymethylated cellulose. The synthesized CMC was characterized, and their physical properties were investigated. The structure of CMC and grafted CMC were investigated by Fourier transform infrared spectroscopy. Findings Solubility, CMC content, degree of substitution and molecular weight of CMC were increased gradually with the increase in the number of reaction steps, although fourth step attained the optimum. The cellulosic waste of knitted rag can easily be used to produce value-added products such as CMC and other cellulose derivatives, and that will ultimately reduce the pollution problems from this waste. Originality/value Grafting of prepared CMC film with methyl methacrylate monomer increased their strength, although decreased rigidity and moisture content because the incorporation of hydrophobic methyl methacrylate monomer was observed.

Influence of CMC Molecular Weight and Degree of Substitution on Clay Swelling Inhibition in Water‐Based Drilling Fluids

SummaryIn this paper, the clay hydration inhibitive properties of carboxymethylcellulose (CMC) in drilling fluids systems were studied. The clay swelling degree was evaluated as a function of time in presence of different aqueous solutions containing sodium chloride, potassium chloride, CMC A (9 × 104 g/mol − DS 0.7), CMC B (2.5 × 105 g/mol − DS 0.7), CMC C (2.5 × 105 g/mol − DS 1.2) and a commercial clay inhibitor based in quaternary amine, that was used as reference pattern. According to results obtained, the low molecular weight CMC showed slightly lower clay swelling degree compared to the high molecular weight along 180 minutes. In parallel, it was confirmed the higher efficiency of quaternary amine‐based commercial inhibitor (QABCI) to control the clay swelling mechanism. Basically, this inhibition effect was attributed to the ability of cationic quaternary ammonium groups to form electrostatic interactions with negatively charged surfaces of the clay, enhancing associative interaction between their particles. Besides, it was visualized by microscopy that the highest molecular weight of CMC provided a reduction in formation and pores size compared to CMC of lower molecular weight after 1,000 minutes in aqueous medium. This behavior could be attributed to the dynamic of interactions between clay and high molecular weight CMC along the time, which is a result of strong contribution of electrostatic interactions between carboxylate groups located along the polymer backbone and positively charged clay layers edges as well as hydrogen bonds.

Effect of CMC Molecular Weight on Acid-Induced Gelation of Heated WPI-CMC Soluble Complex.

Acid-induced gelation properties of heated whey protein isolate (WPI) and carboxymethylcellulose (CMC) soluble complex were investigated as a function of CMC molecular weight (270, 680, and 750 kDa) and concentrations (0% to 0.125%). Heated WPI-CMC soluble complex with 6% protein was made by heating biopolymers together at pH 7.0 and 85 °C for 30 min and diluted to 5% protein before acid-induced gelation. Acid-induced gel formed from heated WPI-CMC complexes exhibited increased hardness and decreased water holding capacity with increasing CMC concentrations but gel strength decreased at higher CMC content. The highest gel strength was observed with CMC 750 k at 0.05%. Gels with low CMC concentration showed homogenous microstructure which was independent of CMC molecular weight, while increasing CMC concentration led to microphase separation with higher CMC molecular weight showing more extensive phase separation. When heated WPI-CMC complexes were prepared at 9% protein the acid gels showed improved gel hardness and water holding capacity, which was supported by the more interconnected protein network with less porosity when compared to complexes heated at 6% protein. It is concluded that protein concentration and biopolymer ratio during complex formation are the major factors affecting gel properties while the effect of CMC molecular weight was less significant.

Characteristics of carboxymethyl cellulose/sericin hydrogels and the influence of molecular weight of carboxymethyl cellulose

Carboxymethyl cellulose (CMC),which is a hydrophilic polysaccharide obtained from the carboxymethylation of natural cellulose, has been formulated as hydrogel for various biomedical applications. However, the functional crosslinking agents were required to form the stable CMC hydrogels. In this study, sericin which is a glue-like protein that envelops the fibroin fiber in the silkworm cocoons was introduced to blend with CMC to form a mechanically stable hydrogel without further crosslinking. Furthermore, the effect of molecular weight of CMC on characteristics of the CMC/sericin hydrogels obtained was investigated. We found that the incorporation of sericin in CMC hydrogels enhanced the stability and the hydrogel’s resistance to hydrolysis and enzymatic degradation while the porous structure and swelling abilities of the CMC hydrogels were preserved. The in vitro biodegradation of the CMC/sericin hydrogels and the release of sericin from the hydrogels were evaluated. The biodegradability of the CMC/sericin hydrogels depended on the molecular weight of CMC. The high molecular weight CMC/sericin hydrogels showed the slowest rate of degradation. The slow-degrading high molecular weight CMC/sericin hydrogels resulted in the lowest amount of sericin release while the fast-degrading low and medium molecular weight CMC/sericin hydrogels released high amount of sericin. The high amount of sericin released from the fast-degrading low and medium molecular weight CMC/sericin hydrogels could consequently promote the collagen production of L929 cells. These CMC/sericin hydrogels could be further investigating to be applied as a wound dressing material. Open image in new window

Functional Polysaccharide Conjugates for the Preparation of Microarrays

A method for the immobilization of functional molecules on cellulose surfaces was developed. The irreversible deposition of the water-soluble polyelectrolyte carboxymethyl cellulose (CMC) on solid cellulose surfaces was used as a basis for this immobilization. CMC was modified using aminofluorescein (AMF) as a model compound for a functional molecule. The carbodiimide mediated coupling efficiency of AMF to CMC was studied in detail, and the functional conjugates were isolated. A quartz crystal microbalance with dissipation was employed to study the immobilization of the functionalized CMC onto cellulose model films in situ. The influence of the carbodiimide concentration, the degree of substitution, and the molecular weight of CMC on the immobilization process was investigated. Atomic force microscopy was used to characterize the changes in the surface morphology of the modified cellulose films. Finally, microspotted arrays of AMF-CMC conjugates were prepared with the knowledge obtained from the basic interaction studies. The successful deposition of AMF-CMC conjugates onto cellulose surfaces was proven by fluorescence microscopy. The conjugation of functional molecules to CMC and the subsequent deposition of these products on cellulose can be seen as a versatile method to immobilize these molecules for applications in the field of microarrays and other sensor surfaces. It offers the possibility to introduce new properties on a variety of cellulosic materials.

Depolymerization of carboxymethylcellulose in a hydro-alcoholic medium by a mono-component endocellulase

Carboxymethylcellulose (CMC) is a cellulose ether with a wide range of applications and markets. In order to tailor the molecular weight and the rheological profile of CMC, the industrial production process often implies a difficult to control depolymerization step with high concentrations of hydrogen peroxide or other oxidizing agents at alkaline pH. Because CMC dissolved in an aqueous buffer at concentrations above 3–4% (w/w) generates extremely high and unmanageable viscosities, we have developed an alternative process of enzymatic depolymerization with a selected, recombinant mono-component endocellulase for the preparation of a highly concentrated aqueous solution of low molecular weight CMC, from a 240–300 kDa CMC dispersed as a slurry in a hydro-alcoholic reaction medium, followed by solvent recovery. Wood cellulose from different tree sources and a few commercially available cellulases, either of natural origin or recombinant, were screened. The recombinant, mono-component endoglucanase Cel12A from T. reesei was selected for CMC hydrolysis carried out in isopropanol. At the end of the reaction, the enzyme is thermally inactivated and the solvent recovered by distillation. This novel industrial process yields a stable aqueous solution of a low viscosity, ready-to-use 35% (w/w) CMC, which is finding increasing new practical applications.

Synergy of CMC and modified chitosan on strength properties of cellulosic fiber network

Previously, the application of modified chitosan (MCN) and carboxymethyl cellulose (CMC) in a dual polymer system showed promising results in increasing the strength of fiber networks. This work evaluates the influence of CMC molecular weight (MW) and of CMC/MCN ratio on the characteristics of formed CMC/MCN complexes in polymer solutions and on the properties of cellulosic fiber networks. The results showed that the application of MCN and the high MW CMC (HCMC) (1:1 charge ratio) enhanced the tensile, burst, and tear indices, but reduced the light scattering coefficient of the fiber network more significantly than that of MCN and the low MW CMC (LCMC). Increasing the ratio of HCMC/MCN marginally affected the tensile index, the burst index, and the light scattering coefficient of the fiber network, even though the ratio significantly affected the characteristics of the CMC/MCN complexes in polymer solutions. The tear index and brightness were improved by increasing the HCMC/MCN ratio. These results were explained based on the retention of HCMC/MCN complexes and the layer-by-layer assembly of HCMC and MCN on the fiber surface.

Topochemical modification of cotton fibres with carboxymethyl cellulose

Adsorption of carboxymethyl cellulose (CMC) as a method to introduce charged (ionizable) groups onto cellulose cotton fibre surfaces was investigated. The method was based on application of a previously published method used for wood fibres. The amount of adsorbed ionizable groups was determined indirectly by analysis of CMC in solution by the phenol–sulphuric acid method and directly by conductometric titration of the fibres. Results from the two methods correlated well. The molecular weight and purity of the CMC had an influence on its adsorption onto cotton; high molecular weight CMC was preferentially adsorbed. The adsorbed charge correlated linearly with the amount of CMC adsorbed. The total charge of the cotton fibres could be increased by more than 50% by adsorption of CMC. It is expected that this modification procedure can be used in a wide spectrum of practical applications.

Untypical rheological behaviour of the lignite–carboxymethylcellulose–water dispersion system

Suspensions of lignite in a solution of a high molecular weight carboxymethylcellulose show peculiar rheological behaviour. Unless the lignite concentration is sufficiently high, apparent viscosity and viscoelastic moduli of the suspension are lower than those of the pure solution. This effect is not suppressed by changing pH and seems to be common for low-concentrated suspensions in solutions of high molecular weight (bio)polymer. It is explained by specific structuring of the suspensions. Lignite particles at lower concentration separate long cellulose chains and facilitate their movement under shear flow. The particles loosen inter-chain contacts, disturb and release elastic gel-like structure formed by the long cellulose chains, which results in the low strain oscillatory deformation, the decrease in the moduli and the increase in the loss angle. If the amount of lignite particles is sufficiently high, suspension stiffening occurs as usual. No such effect was observed for suspensions prepared from the low molecular weight derivative.

The effect of molecular weight and degree of substitution on the interactions between carboxymethyl cellulose and cetyltrimethylammonium bromide

The behavior of mixtures of carboxymethyl cellulose (CMC) and the cationic surfactant cetyltrimethylammonium bromide (CTAB) was investigated in the dilute range at the liquid–air interface by means of surface tension and ellipsometry, and in the bulk solution by conductivity and turbidity measurements. CMC behaves like a polyanion under the experimental conditions (pH ∼ 7.5). The effect of the CMC molecular weight and degree of substitution on the complexation with CTAB was studied. Keeping the CMC concentration constant at 1.0 g/L, we observed three critical concentrations as the CTAB concentration was increased. Only the CMC degree of substitution (DS) exerted influence on the critical concentration values, evidencing the cooperative binding and the electrostatic interaction as the main driving forces for the complex formation. The critical concentration values found at the liquid–air interface are in accordance with those determined in the bulk solution. The co-adsorption of CMC and CTAB was observed at the liquid–air interface, where the molecular packing became denser with increasing CTAB concentration.

The effect of chemical composition and molecular weight of polysaccharide depressants on the flotation of talc

Polysaccharide reagents are frequently used in the mineral processing industry to improve the grade of the concentrate by depressing the naturally floatable gangue. A microflotation study showed that at an ionic strength of 10 −3 M KNO 3, the dosage, molecular weight, and chemical composition of polysaccharide depressants affect their depressing action on talc. Viscosity readings for four carboxymethylcellulose (CMC) reagents and three modified guar gum reagents are reported, and estimates of the molecular weight of the CMCs are calculated. The natural floatability of talc was diminished when guar-based polymers were added to the system. Moreover, the depression of talc was increased as the guar molecular weight was increased. Strong depression of talc was achieved at a relatively low guar dosage; higher dosages did not further increase this depression. At 10 −3 M KNO 3, the CMCs were ineffective depressants of talc. No systematic change in talc depression for differing molecular weight CMCs was observed. A small increase in depression was observed when the concentration of CMC was increased. A mechanism is proposed for the polymer–talc interactions based on these preliminary studies and information from similar studies in literature.

Solvent effect on carboxymethylation of cellulose

The relationship between the composition of the solvent (water/isopropyl alcohol) and the degree of substitution, viscosity and molecular weight of carboxymethylcellulose (CMC) is investigated. It is found that the alcohol facilitates the destruction of cellulose crystalline structure and the diffusion of the small reagent molecules into the cellulose, which elevates the availability of the reagent for etherification. Because of the weak polarizability of isopropyl alcohol, it helps to keep the the cellulose molecules to be less decomposed by alkali. This results in the increase of the degree of substitution for the CMC and effects the CMC's high resistance to alkali

The influence of the molecular weight of carboxymethyl cellulose (CMC) on rheology, dewatering and coating performance

Article The influence of the molecular weight of carboxymethyl cellulose (CMC) on rheology, dewatering and coating performance was published on January 1, 1993 in the journal Nordic Pulp & Paper Research Journal (volume 8, issue 1).