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Carboxylmethyl cellulose = CMC
CAS No. : 9004-32-4
EC / List No: 618-378-6
Carboxyl methyl cellulose (CMC) or cellulose gum is a cellulose derivative with Carboxyl methyl cellulose (-CH2-COOH) bound to some of the hydroxyl groups of the glucopyranose monomers that make up the cellulose backbone.
Carboxyl methyl cellulose often used as its sodium salt, sodium carboxy methyl cellulose.
Carboxyl methyl cellulose used to be marketed under the name Tylose, a registered trademark of SE Tylose.
Carboxyl methyl cellulose synthesized by the alkali-catalyzed reaction of cellulose with chloroacetic acid.
The polar (organic acid) carboxyl groups render the cellulose soluble and chemically reactive.
Following the initial reaction, the resultant mixture produces about 60% Carboxy methyl cellulose plus 40% salts (sodium chloride and sodium glycolate).
This product is the so-called technical Carboxyl methyl cellulose which is used in detergents.
A further purification process is used to remove these salts to produce the pure Carboxyl methyl cellulose used for food, pharmaceutical, and dentifrice (toothpaste) applications.
An intermediate "semipurified" grade is also produced, typically used in paper applications such as restoration of archival documents.
The functional properties of Carboxyl methyl cellulose depend on the degree of substitution of the cellulose structure , as well as the chain length of the cellulose backbone structure and the degree of clustering of the carboxymethyl substituents.
Carboxyl methyl cellulose is used in food under the E number E466 or E469 (when it is enzymatically hydrolyzed) as a viscosity modifier or thickener, and to stabilize emulsions in various products including ice cream.
Carboxyl methyl cellulose also a constituent of many non-food products, such as toothpaste, laxatives, diet pills, water-based paints, detergents, textile sizing, reusable heat packs, and various paper products.
Carboxyl methyl cellulose used primarily because it has high viscosity, is nontoxic, and is generally considered to be hypoallergenic as the major source fiber is either softwood pulp or cotton linter.
Carboxyl methyl cellulose is used extensively in gluten free and reduced fat food products.
In laundry detergents,Carboxyl methyl cellulose used as a soil suspension polymer designed to deposit onto cotton and other cellulosic fabrics, creating a negatively charged barrier to soils in the wash solution.
In ophthalmology, Carboxyl methyl cellulose is used as a lubricant in artificial tears to treat dry eyes.
Extensive treatment may be required to treat severe dry eye syndrome or Meibomian gland dysfunction (MGD).
Carboxyl methyl cellulose is also used as a thickening agent, for example, in the oil-drilling industry as an ingredient of drilling mud, where it acts as a viscosity modifier and water retention agent.
Sodium Carboxyl methyl cellulose (Na CMC) for example, is used as a negative control agent for alopecia in rabbits.
Knitted fabric made of cellulose (e.g. cotton or viscose rayon) may be converted into Carboxyl methyl cellulose and used in various medical applications.[citation needed]
Device for epistaxis (nose bleeding). A poly-vinyl chloride (PVC) balloon is covered by Carboxyl methyl cellulose knitted fabric reinforced by nylon.
The device is soaked in water to form a gel, this is inserted into the nose and the balloon inflated.
The combination of the inflated balloon and the therapeutic effect of the Carboxyl methyl cellulose stops the bleeding.
Fabric used as a dressing following ear nose and throat surgical procedures.
Water is added to form a gel, and this gel is inserted into the sinus cavity following surgery.
Insoluble microgranular Carboxy methyl cellulose is used as a cation-exchange resin in ion-exchange chromatography for purification of proteins.
Presumably, the level of derivatization is much lower, so the solubility properties of microgranular cellulose are retained, while adding sufficient negatively charged carboxylate groups to bind to positively charged proteins.
Carboxyl methyl cellulose is also used in ice packs to form a eutectic mixture resulting in a lower freezing point, and therefore more cooling capacity than ice.
Aqueous solutions of Carboxyl methyl cellulose have also been used to disperse carbon nanotubes.
The long Carboxyl methyl cellulose molecules are thought to wrap around the nanotubes, allowing them to be dispersed in water.
In conservation-restoration, it is used as an adhesive or fixative (commercial name Walocel, Klucel).
Carboxyl methyl cellulose is used to achieve tartrate or cold stability in wine.
This innovation may save megawatts of electricity used to chill wine in warm climates.
Carboxyl methyl cellulose more stable than metatartaric acid and is very effective in inhibiting tartrate precipitation.
Carboxyl methyl cellulose reported that KHT crystals, in presence of CMC, grow slower and change their morphology.
Their shape becomes flatter because they lose 2 of the 7 faces, changing their dimensions.
Carboxyl methyl cellulose molecules, negatively charged at wine pH, interact with the electropositive surface of the crystals, where potassium ions are accumulated.
The slower growth of the crystals and the modification of their shape are caused by the competition between Carboxyl methyl cellulose molecules and bitartrate ions for binding to the KHT crystals.
In veterinary medicine , Carboxyl methyl cellulose is used in abdominal surgeries in large animals, particularly horses, to prevent the formation of bowel adhesions.
Carboxyl methyl cellulose is sometimes used as an electrode binder in advanced battery applications (i.e. lithium ion batteries), especially with graphite anodes.
Carboxyl methyl cellulose's water solubility allows for less toxic and costly processing than with non-water-soluble binders, like the traditional polyvinylidene fluoride (PVDF), which requires toxic n-methylpyrrolidone (NMP) for processing.
Carboxyl methyl cellulose is often used in conjunction with styrene-butadiene rubber (SBR) for electrodes requiring extra flexibility, e.g. for use with silicon-containing anodes.
Carboxyl methyl cellulose powder is widely used in the ice cream industry, to make ice creams without churning or extreme low temperatures, thereby eliminating the need for the conventional churners or salt ice mixes.
Carboxyl methyl cellulose is used in preparing bakery products such as bread and cake.
The use of Carboxyl methyl cellulose gives the loaf a much improved quality at a reduced cost to the baker, by economizing on the fat component.
Carboxy methyl cellulose is also used as an emulsifier in high quality biscuits.
By dispersing fat uniformly in the dough, it improves the release of the dough from the moulds and cutters, achieving well-shaped biscuits without any distorted edges.
Carboxyl methyl cellulose can also help to reduce the amount of egg yolk or fat used in making the biscuits, thus achieving economy.
Use of Carboxyl methyl cellulose in candy preparation ensures smooth dispersion in flavour oils, and improves texture and quality.
Carboxyl methyl cellulose is used in chewing gums, margarines and peanut butter as an emulsifier. It is also used in leather crafting to burnish the edges.
Carboxyl methyl cellulose has also been used extensively to characterize enzyme activity from endoglucanases (part of the cellulase complex).
Carboxyl methyl cellulose is a highly specific substrate for endo-acting cellulases, as its structure has been engineered to decrystallize cellulose and create amorphous sites that are ideal for endoglucanase action.
Carboxyl methyl cellulose is desirable because the catalysis product (glucose) is easily measured using a reducing sugar assay, such as 3,5-dinitrosalicylic acid.
Using Carboxy methyl cellulose in enzyme assays is especially important in regard to screening for cellulase enzymes that are needed for more efficient cellulosic ethanol conversion.
However, Carboxyl methyl cellulose has also been misused in earlier work with cellulase enzymes, as many had associated whole cellulase activity with CMC hydrolysis.
As the mechanism of cellulose depolymerization has become better understood, exo-cellulases are dominant in the degradation of crystalline (e.g. Avicel) and not soluble (e.g. CMC) cellulose.
Carboxyl methyl cellulose is a derivative of cellulose, containing Carboxyl methyl cellulose groups that are generated via the reaction of cellulose with chloroacetate in alkali to produce substitutions in the C2, C3, or C6 positions of glucose units .
As a result, Carboxyl methyl cellulose is water soluble and more amenable to the hydrolytic activity of cellulases.
Carboxyl methyl cellulose is therefore a useful additive to both liquid and solid medium for the detection of cellulase activity, and its hydrolysis can be subsequently determined by the use of the dye Congo red, which binds to intact β-d-glucans.
Zones of clearing around colonies growing on solid medium containing Carboxyl methyl cellulose, subsequently stained with Congo red, provides a useful assay for detecting hydrolysis of Carboxyl methyl cellulose and therefore, β-d-glucanase activity .
The inoculation of isolates onto membrane filters placed on the surface of Carboxyl methyl cellulose agar plates is a useful modification of this technique, as the filter may subsequently be removed allowing visualization of clear zones in the agar underneath cellulolytic colonies.
Carboxyl methyl cellulose (CMC), a derivative of cellulose , is a cheaper, nontoxic, biodegradable, and renewable polymer.
The drawback of Carboxyl methyl cellulose film is its poor mechanical properties.
Due to its superior mechanical properties, low flammability, impressive biocompatibility, and greater biodegradability, silk fibroin has been identified as a potentially convenient biomaterial.
Depending on the requirements for various applications it can be modified to a hydrogel, film, scaffold, or nonwoven mat .
GO is a suitable filler in composites that enhances the mechanical properties .
Abdulkhani et al.
synthesized biopolymer nanocomposite films by mixing reduced graphene oxide (RGO) to sodium carboxy methyl cellulose (Carboxyl methly cellulose)/silk fibroin matrix.
The result showed that RGO is useful for composites due to its high performance and low cost.
These nanocomposites are used in food packaging.
Carboxyl methyl cellulose sodium is a viscous polysaccharide that belongs to a high molecular weight category.
Carboxyl methyl cellulose has mucoadhesive property and is used during eye surgery.
Carboxyl methyl cellulose sodium promotes re-epithelialization of the epithelial cells in corneal wounds.
Carboxyl methyl cellulose useful for the study of attached cell and three-dimensional tissue culture models.
Carboxyl methyl cellulose sodium has been used as a vehicle for tamoxifen citrate, sorafenib, and savolitinib.
Carboxyl methyl cellulose has also been used as a component of serum-free medium (SFM) for the suspension of human umbilical vein endothelial spheroids.
Useful for the study of attached cell and three-dimensional tissue culture models.
Pharmaceutical secondary standards for application in quality control provide pharma laboratories and manufacturers with a convenient and cost-effective alternative to the preparation of in-house working standards.
Sodium carboxy methyl cellulose (Na CMC) is used for its thickening and swelling properties in a wide range of complex formulated products for pharmaceutical, food, home, and personal care applications, as well as in paper, water treatment, and mineral processing industries.
To design Na Carboxyl methyl cellulose solutions for applications, a detailed understanding of the concentration-dependent rheology and relaxation response is needed.
We address this here by investigating aqueous Na CMC solutions over a wide range of concentrations using rheology as well as static and dynamic light scattering.
The concentration dependence of the solution specific viscosities ηsp could be described using a set of three power laws, as predicted from the scaling theory of polyelectrolytes.
Alternatively, a simpler approach could be used, which interpolates between two power law regimes and introduces only one characteristic crossover concentration.
We interpret the observed behavior as a transition from the semidilute nonentangled to the entangled concentration regimes; this transition behavior was not observed in the solution structure, as determined using static light scattering.
Dynamic light scattering revealed three relaxation modes.
The two fastest relaxations were assigned as the “fast” and “slow” relaxation modes typically observed in salt-free or not fully screened polyelectrolyte solutions within the semidilute concentration range.
The third, typically weak mode, was attributed to the presence of a small amount of poorly dissolved cellulose residuals.
Since filtration altered the solution behavior, without sufficiently removing the residuals, data collection and processing were adapted to account for this, which facilitated a detailed light scattering investigation of the original solutions, relevant for industrial applications.
The relaxation time characterizing the fast mode, τf, was concentration independent; whereas the relaxation time of the slow mode, τs, demonstrated similar crossover behavior as observed for the specific viscosity, further demonstrating the dynamic nature of the crossover.
Examples of particulates observed in Na Carboxyl methyl cellulose solutions under the microscope;
small particulates observed in a 0.018 wt % Na Carboxyl methyl cellulose solution;
examples of particulates observed with a phase contrast microscope in microcrystalline cellulose suspensions;
examples of viscosity curves across the studied range of concentrations;
illustration of the methods used to calculate the crossover concentrations;
influence of the measurement duration on the light scattering data collected for a 0.073 wt % Na Carboxy methyl cellulose solution;
scattered intensity (or count rate) as a function of time for a 0.073 wt % Na Carboxyl methly cellulose solution at θ = 30° and for Δtmeas = 10 min;
illustration of the method used to process the DLS data collected at an angle θ;
measurement reproducibility and data processing for low Na Carboxyl methyl cellulose concentrations (0.073 wt %), intermediate Na CMC concentrations (0.37 wt %), and high Na CMC concentrations (0.55 wt %);
residuals of the fits shown in Figure S9;
comparison between the excess Rayleigh ratio ΔR values obtained during SLS and DLS measurements (i.e., short and long measurements, respectively);
refractive index as a function of Na Carboxyl methyl celluloseconcentration;
determination of the excess Rayleigh ratio at q2 = 0 for the 0.046 wt % Na CMC solution;
q- and cNa Carboxyl methyl cellulose-dependences of the ratio of the excess Rayleigh contributions of the slow and the fast modes ΔRs/ΔRf;
normalized intensity autocorrelation data over the full range of concentrations at three different scattering angles;
q- and cNa Carboxyl methyl cellulose-dependences of the fast mode contribution to the excess Rayleigh ratio scattering;
illustration of the calculation of the fast mode diffusion coefficient Df with the 0.92 wt % Na CMC solution;
q- and cNa Carboxyl methyl cellulose-dependences of the slow mode contribution to the excess Rayleigh ratio scattering;
concentration-dependence of the power law exponents of τs = f(q);
concentration and angle dependence of the slow mode relaxation time τs;
illustration of the calculation of the slow mode diffusion coefficient Ds with the 0.046 wt % Na Carboxy methyl cellulose solution;
illustration of the calculation of the slow mode diffusion coefficient Ds with the 0.18 wt % Na Carboxy methyl cellulose solution;
concentration dependence of the slow mode diffusion coefficient Ds calculated using four different methods;
apparent hydrodynamic radius RH,app and apparent radius of gyration Rg,app of the domains as a function of Na Carboxyl methyl cellulose concentration.
Solubility:
Freely soluble in water, insoluble in ethanol
Viscosity (60% solids):
Not less than 2500 mPas corresponding to an average molecular weight of 5000 D
Loss on drying:
Not more than 12% (105° to constant weight)
pH:
Not less than 6.0 and not more than 8.5 (1 in 100 solution)
Polyaniline (PANi) is a conducting polymer which has been subject of intensive research on the exploitation of new products and applications.
The main aim of the work is the development of a conductive bacterial cellulose (BC)-based material by enzymatic-assisted polymerization of aniline.
For this, we study the role of carboxy methyl cellulose (CMC) as a template for the in situ polymerization of aniline.
Bacterial cellulose was used as the supporting material for the entrapment of CMC and for the in situ oxidation reactions.
The amount of Carboxyl methyl cellulose entrapped inside BC was optimized as well as the conditions for laccase-assisted oxidation of aniline.
The new oligomers were evaluated by spectrometric techniques, namely 1H NMR and MALDI-TOF, and the functionalized BC surfaces were analyzed by thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), and reflectance spectrophotometry.
The conductivity of the developed materials was evaluated using the four-probe methodology.
The oligomers obtained after reaction in the presence of CMC as template display a similar structure as when the reaction is conducted only in BC.
Though, after oxidation in the presence of this template, the amount of oligomers entrapped inside BC/CMC is considerably higher conferring to the material greater electrical conductivity and coloration.
The use of Carboxyl methyl cellulose as a template for aniline oxidation on BC seems to be a promising and cheap strategy to improve the yield of functionalization and increment the properties of the materials, namely electrical conductivity and coloration.
Conductive materials have been gaining scientific attention due to the increasing need for new technologies for the exploitation of electronic sensor devices, energy-storage, and intelligent clothing .
Bacterial cellulose (BC) has been used to develop composites containing a conductive polymer, such as polyaniline (PANi), polypyrrole and polythiophene, and others .
The use of templates, like sulfonated polystyrene as sodium salt (SPS), the calcium salt of ligninosulfonate, micelles composed by sodium dodecylbenzenesulfonate (SDBS), or vesicles made-up of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) have been described as favoring the polymerization of aniline .
These molecules are composed by sulfonate groups and, in oxidation conditions, aniline is oxidized to a conductive product, emeraldine salt .
The templates, due to a localization of the reaction in their vicinity, direct the regioselectivity of the monomer coupling reaction, favoring para-over ortho-coupling of oxidized aniline.
These compounds have dopant action (counter ions), which balance the positive charge on the PANi, thereby stabilizing the PANi-Emeraldine salt structure, crucial for electrical conductivity.
Together with templates, the laccase/O2- assisted polymerization of aniline has been studied as an environmentally friendly route to produce conductive PANi .
Laccase has been applied for the aniline polymerization in situ inside BC nano fibers under mild conditions replacing the chemical oxidants that are normally used, such as ammonium peroxydisulfate, potassium dichromate or ferric chloride .
The use of templates is crucial to reduce the undesired coupling reactions, as side-chain branching, and to ensure the polymerization of linear head-to-tail aniline .
The template works by forming polymer–polymer complexes which are stabilized via non-covalent binding forces among hydrogen bonds, electrostatic and hydrophobic interactions during polymerization .
Carboxyl methyl cellulose (CMC), a soluble derivative of cellulose, is an example of an efficient template for aniline polymerization.
Carboxyl methyl cellulose adsorbs irreversibly to cellulose fibers under specific conditions increasing their negative charge .
Carboxyl methyl cellulose contains –COO– groups which supply anionic locations to react with electropositive molecules (positively charged cations) via electrostatic interactions, favoring the polymerization of aniline .
BC has considerable amount of hydroxyl groups which, due to their high reactivity, can be easily modified.
However, the reactivity of the hydroxyl groups can be restricted by intramolecular and intermolecular hydrogen bonds during polymerization events .
When Carboxyl methyl cellulose is introduced inside BC, the –COO– groups of Carboxyl methyl cellulose can form intermolecular interactions with the hydroxyl groups of BC.
The loss of some –OH groups by BC, able to interact with other compounds, can be counterbalanced by the presence of Carboxyl methyl cellulose, which is composed by hydroxyl and carboxylate groups.
In this work, we developed conductive BC composites by entrapping Carboxyl methyl cellulose inside BC membranes followed by the in situ aniline polymerization by laccase.
The Carboxyl methyl cellulose was entrapped inside BC to serve as template for polymerization and laccase was used as reaction catalyst.
Potassium hexacyanoferrate (II) (KHCF), a radical initiator, and bis(2-ethylhexyl) sulfosuccinate sodium salt (AOT), a surfactant, were used as additives for aniline oxidation.
The role of Carboxyl methyl cellulose on aniline polymerization was evaluated through the quantification of the amount of polymer formed.
The polymerization of aniline was evaluated by UV/Visible spectroscopy and the new oligomers were characterized by spectrometric techniques, namely 1H NMR and MALDI-TOF.
BC/PANi and BC/CMC/PANi composites were monitored by FTIR, SEM, TGA, and XRD analysis.
The conductivity of the developed materials was assessed through the four-probe method and the color of BC samples was evaluated spectrophotometrically.
The linear polymer carboxy methyl cellulose (CMC) as a polyelectrolyte is an object of consideration in this review.
The emphasis is on the electric properties of Carboxy methyl cellulose both as a free chain in solution and adsorbed on the solid surface.
A special attention is paid to the mobility of counterions, electrostatically associated with the CMC polyelectrolyte chain
Carboxy methyl cellulose [C6H7O(OH)3−x(OCH2COOH)x]n is a derivative of the regenerated cellulose [C6H10O5]n with hydroxy-acetic acid (hydroxy ethanoic acid) CH2(OH)COOH or sodium monochloroacetate ClCH2COONa.
The CMC backbone consist of D-glucose residues linked by β-1,4-linkage.
The molecular mass of one glucose unit in CMC chain is mCMC = 146.14 + 75.04 x, where x ≤ 3 is the degree of substitution (DS).
As a rule CMC is produced as sodium salt [C6H7O(OH)3−x(OCH2COONa)x]n with DS = 0.4−1.2, then the molecular mass per unit is mNaCMC = 146.14 + 97.03 x ≈ 185−263 g/mol.
As derivative of the cellulose (poly-β-D-glucose) Carboxy methyl cellulose has inherited its main structural peculiarities:
(a) rigidity of the glucose units (6-atoms rings in “armchair” conformation);
(b) an almost fully extended conformation owing to impossibility for rotation round the C−O−C bonds between the glucose residues because of strong steric limitations (a consequence of the β-configuration at C-1 atom in 1,4-linkage);
and (c) orientation of the bigger constituent groups (−OH, −CH2OH and −OCH2COOH) in the equatorial plane out of the saccharic ring.
The cross-sectional dimension of the Carboxy methyl cellulose chain is a sum of the diameter of the glucose ring (0.5 nm) and the size of the carboxymethyl group (0.4 nm, situated on the both side of the chain); the effective diameter of the chain is rather higher because the glucose residues are oriented not line in line but somewhat tilted along the backbone line .
The replacement of the H-atom of −OH-group with −CH2COO− causes a loss of the possibility of parallel association of Carboxy methyl cellulose chains in sheet-like structures (a characteristic of the cellulose structure leading to supramolecular organization in microfibrils ) because of both steric hindrance and electrostatic repulsion but that does not exclude the possibility of intra- and intermolecular interaction by hydrogen bonds between the unsubstituted −OH groups.
In the literature the polymer unit of Carboxyl methyl cellulose chain is denoted as consisting of one or two glucose rings following the manner applying to the cellulose.
The one unit way is chemically well-founded according the cellulose contents because all the glucose units are chemically identical (except those on the two ends of the chain).
According to the conformation of the cellulose chain a more thought-out manner is the two glucose residues unit because this way allows distinguishing the cellulose (poly-β-D-glucose) and the amylose (poly-α-D-glucose), both linear chains of chemically identical glucose residues.
The conformation of the polymer chains of these two polysaccharides differs drastically owing to the configuration at the anomeric C-1 atom: the β-1,4-linkage in the cellulose leads to inversed orientation of every second glucose ring according the previous one and to sterically conditioned full extended conformation because of impossible rotation round the C−O−C bonds between C-1 and C-4 atoms of the neighbour rings.
In the case of the amylose the α-configuration at C-1 atom leads to uniform orientation of the glucose rings and to impossibility of extended conformation; due to the α-1,4-linkage amylose chain has a tendency to spiral conformation .
Since the linear charge density of the CMC chain is determined by the number of −COO− groups per glucose unit independently of its orientation, in this chapter the one glucose residue is accepted to denote the monomeric unit.
The −CH2COOH group can be attached to every of the three hydroxyl groups of the cellulose monomer unit, so theoretically the degree of substitution (DS) can reach 3, but usually DS does not exceed 2. The distribution of −CH2COOH groups in the glucose unit and along the CMC chain is accepted to be random in the model proposed to give the monomer composition of a sample with known DS.
The model is based on the supposition that the substitute reaction occurs at random, i.e. each of the three −OH groups (at C-2, C-3 and C-6 position) of every monomer unit can be substituted in equal probability independently on the presence of another constituent in the same glucose unit.
The experimental investigations of the mole fraction of substituted monomers of CMC confirm the hypothesis for random distribution of the constituents.
For example, at DS = 1.3 the mole fractions are about 0.2, 0.4, 0.3 and 0.1 for unsubstituted, mono-, di- and trisubstituted, respectively.
On the base of these results it can be concluded that the −CH2COO− groups are also randomly distributed along the CMC chain and practically there are no regions containing more than one or two uncharged monomer units when DS is higher than 1−2.
The absence of long uncharged segments allows accepting that the negative charges are almost evenly distributed along the CMC chain at high linear charge density (high DS and high degree of dissociation); that is important condition for applying the model of uniformly charged cylinder to CMC chain.
The distance between two glucose units in CMC chain is 0.515 nm .
The contour length Lc (the length of the chain backbone if it is fully stretched but without deformation of the valence angles and bonds) is determined as a product of the number of monomers n and the length of one unit: Lc = 0.515 n (nm).
In this section the characteristics of CMC as a free polyelectrolyte chain are overlooked, i.e. the chain has conformational freedom that does not or depends on the presence of other macromolecules, respectively in diluted solution or semi-concentrated ones.
The chain is immersed in salt-free medium or in electrolyte with valency z. In the first case the counterions originate from the ionizable group of the chain:
H+ or Na+ (in the case of CMC or its sodium salt NaCMC).
A part of counterions can be electrostatically adsorbed losing their freedom; the rest are scattered by the thermal energy kT and are randomly distributed around the chain forming an ions cloud.
The effective dissociation constant Ka (respectively pKa = −logKa) of a weak polyelectrolyte depends on the neighbour electric charges in the chain and in the medium.
The presence of other negative charges in the vicinity of a given COO− group leads to increasing of the electric field intensity and the local concentration of H3O+ ions.
As a result the probability of protonation of the COO− group increases; respectively the equilibrium of the reaction COOH↔COO− +H+ is shifted to the non-dissociated form.
That is why the dissociation capability of the ionizable groups in the polyelectrolyte chain can not be characterized by a constant like in the case of a simple (monomeric) acid (pKa = pH at α = 1/2).
The apparent (effective) dissociation “constant” pKa = f(x,α,μ) of COOH groups in CMC chain is a function of the degree of substitution x, the degree of dissociation α (determined by pH of the medium), and the ionic strength μ; the first two factors determine the linear charge density of the chain.
Methylcellulose (MC) and sodium carboxyl methyl cellulose (sod. CMC) have many other uses besides those in conservation.
A brief rummage through your medicine cabinet may come up with such products as toothpaste, laxatives, or diet pills each of which may contain either MC or sod. Carboxyl methyl cellulose.
Other products include ice cream, water-based paints, detergents and a variety of paper products to name but a few.
Characteristics which make them useful are: high viscosity in low concentrations, defoaming abilities, surfactant, and bulking abilities.
They are not toxic and do not promote allergic reactions in humans
These cellulose polymers can be purchased in grades ranging from coarse to fine particles and in varying viscosities.
In solution, Hercules Carboxyl methyl cellulose 7H and Culminal (MC from Talas) are quite clear while Cellofas B3500 from Conservation Materials is hazy.
The easiest way to make up any of the MCs or sod.
Carboxyl methyl celluloses is to measure out the desired quantity of the powder, fill a blender with the right amount of deionized or distilled water, turn on the blender to the lowest speed, and pour the powder in a steady stream into the vortex.
As soon as all of the powder is in the water, turn off the blender.
Over-blending can result in a loss of viscosity.
No preservative is necessary as long as purified water is used and the storage container is airtight.
After blending, Carboxyl methyl cellulose best to leave the solution at least one hour before using.
Most conservators regard the MCs and sod.
Carboxyl methyl celluloses primarily as adhesives. We will see in fact that they have many other uses, but let's start with their adhesive applications.
Carboxyl methyl cellulose alone is really strong enough to be used as an adhesive when a great deal of stress on the bond is encountered such as in tear repairs or hinges.
MC should also not be used for an overall backing as it is not a very polar adhesive and as such will not affect a very good bond between papers, especially smooth-surfaced papers.
Carboxyl methyl cellulose occasionally mixed with wheat starch paste in order to provide 'slip' and indeed this mixture comprises most wallpaper pastes. Sod.
Carboxyl methyl cellulose on the other hand is a very polar adhesive and as such makes a very good bond between sheets of paper and is useful for overall backings where stress on the bond is not a real problem.
Carboxyl methyl cellulose could also be mixed with wheat starch paste to provide 'slip'.
The advantage sod.
Carboxyl methyl cellulose has over wheat starch paste is that a dry backing can be done when the original work of art consists of water sensitive media or paper which is dimensionally unstable.
This is because a 2.5% solution of say CMC 7H is very viscous but is not very 'wet' so that it can be brushed on the reverse of the original and the backing paper without either expanding too much or without much water penetrating to the surface of the origi al.
Once the backing is complete, air drying can take place with the original face down so that water evaporates from the back reducing still further the risk of the front getting wet.
When dry the backed original can be humidified and pressed or put out on a drying screen/board to flatten.
The adhesive dries to a very thin even layer and is easily reversible with cold water.
Carboxyl methyl cellulose non-staining and does not become brittle upon ageing. Other applications in this section might include temporary facings, mends or backings.
If you can use hot water for a wash bath, you might like to use MC as the temporary adhesive as it will not dissolve in hot water but is easily reversed in cold water.
This would probably hold together a badly torn piece which could not be handled in any other way.
An extremely useful method for quickly filling small holes or losses in paper is accomplished by mixing Whatman Cellulose Powder CF11 with MC or sod.Carboxyl methyl cellulose.
The cellulose powder as sold is very white, but gradations of browns can be made by cooking the dry powder in a Teflon pan over a hot plate.
Wear a dust mask as the powder can be irritating if inhaled.
Also be careful not to scorch the powder.
The cooked powder can then be color matched, dry, to the original paper by adding lighter or darker shades of the powder as necessary.
Then enough 3% MC or 2.5% sod. CMC is added to make a stiff paste.
Carboxyl methyl cellulose can then be applied to the hole or loss with a microspatula, tip of a scalpel blade, etc. Leave it to air dry. Retouching is seldom necessary if you have matched the powder color well in the first place.
If a smoother surface is needed, small amounts of calcium carbonate can be added to the powder before the adhesive is added.
Any excess of the cellulose powder paste left over can be allowed to dry out, and later on, rejuvenated for further use by adding a few drops of water and working up into a paste again.
These cellulose polymers also act as deflocculating agents in that they cause particles such as fibers to stay in suspension and not clump together and separate out of solution.
This advantage can be very useful in employing wet pulp fills in a treatment, especially when using a pipette to distribute the pulp from the slurry.
The proportions are about 1:3, .5% MC or sod.
Carboxyl methyl cellulose: pulp slurry.
In low concentrations such as .5%, these polymers can serve very well as sizing agents and indeed are used extensively in the paper industry as both internal and surface sizes.
In paper conservation, the use of a sizing agent can perform two roles: to repel oil and/or grease and to enhance the fiber-to-fiber bonding which makes the paper stronger and more durable.
The .5% solutions of either MC or sod. CMC can be brushed on both sides of the non-water sensitive original through tissue paper on silicone paper and left to air dry.
They could also be brushed on the surfaces while the piece was on the vacuum suction table to enhance penetration.
This should be done on a porous yet slick-surface material such as Hollytex, Reemay or Pellon and allowed to air dry.
Because of its surfactant properties, MC and sod.
Carboxyl methyl cellulose can be used like detergents.
If a swab is dipped in the viscous solution and the excess wiped off, it can be used as a kind of cleaning lubricant over areas of dirt and/or staining with little or no risk of abrading the paper.
Excess on the paper surface should be removed when the treatment is complete as both MC and sod. CMC will leave a slightly greyish film.
In conjunction with this surfactant property and because 3% or 2.5% solutions carry a lot of water but are not wet, these polymers can be used as poultice material to soak up staining, soften adhesives through paper (even varnished paper), aid in removing old adhesive residues without affecting water sensitive media, and can act as a viscous carrier for enzymes, bleach and solvents.
IUPAC NAME :
2,3,4,5,6-pentahydroxyhexanal acetic acid sodium hydride,
acetic acid; 2,3,4,5,6-pentahydroxyhexanal; sodium
Carboximethilcelullose
Carboxymethyl cellulose
Carboxymethyl Cellulose Sodium
Carboxymethyl cellulose sodium salt
Carboxymethyl cellulose, sodium salt
Carboxymethylcellulose
carboxymethylcellulose
Cellulose carboxymethyl ether sodium salt
synonyms:
Acétate de sodium - hexose (1:1:1)
Natriumacetat -hexose (1:1:1)
Sodium acetate - hexose (1:1:1)
