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Sodium carboxymethyl cellulose (sodium CMC, often shortened to CMC) is a water-soluble, anionic cellulose derivative produced by etherification of cellulose with monochloroacetic acid (or its salts). CMC is a versatile hydrocolloid used worldwide as a thickener, stabilizer, binder, film former and rheology modifier across food, pharmaceuticals, cosmetics, paper, textiles, detergents, construction and emerging high-tech applications
Also known as: Carboxymethyl cellulose sodium, CMC-Na, sodium CMC, cellulose gum.
Main CAS number: 9004-32-4.
Chemical structure and basic chemistry
CMC is produced by introducing carboxymethyl (–CH2–COO–) substituents onto the hydroxyl groups of the cellulose backbone (β-1,4 linked D-glucopyranose units).
The substitution results in the sodium salt form (–CH2–COO⁻ Na⁺) when prepared under alkaline conditions with sodium monochloroacetate or monochloroacetate salts. Key structural parameters:
Degree of substitution (DS): average number of substituents per anhydroglucose unit (AGU); theoretical maximum DS = 3.0.
Practical commercial DS for soluble CMC typically ranges ~0.6–1.2 (commonly 0.6–0.95 for many food/pharma grades).
DS strongly affects solubility, charge density and water-binding.
Molecular weight / degree of polymerization (DP): CMC is a polymeric material; commercial Mw spans from ~20,000 up to several million Da—practically characterized by intrinsic viscosity or solution viscosity rather than single Mw.
Viscosity grades (low, medium, high) are commonly used to specify functional behavior.
Anionic character: The carboxylate groups impart anionic charge, enabling electrolyte sensitivity, pH dependence, and interactions with cationic polymers or multivalent cations.
Manufacturing (industrial production routes)
Typical industrial production proceeds in two main stages:
Alkalization (activation) — cellulose (wood pulp, cotton linter or other cellulosic feedstock) is slurried in alkali (sodium hydroxide).
Alkali swells fibers and creates reactive alkoxide sites (–O⁻ Na⁺) on cellulose.
Etherification — the alkali-activated cellulose reacts with monochloroacetic acid (MCA) or sodium monochloroacetate (SMCA) to introduce carboxymethyl groups.
Reaction conditions (temperature, MCA/NaOH ratio, solvent/media, time) determine DS and side reactions (e.g., glycolate formation).
After reaction, product is neutralized, washed (to remove salts and residual reagents), and dried and milled to powder.
Control of particle size and residual salt content is important for grade definition (industrial vs food-grade).
Process variants and critical parameters:
Choice of cellulose feedstock: purity and degree of polymerization affect final CMC properties and yield.
Alkali concentration and reaction stoichiometry: higher NaOH and MCA ratios increase DS but can increase degradation.
Solvent systems: typical process uses aqueous media; some processes include isopropanol or ethanol for better control of swelling and substitution.
Washing and desalting: removal of sodium chloride (formed as byproduct) and unreacted reagents is critical for food and pharmaceutical grades.
Physico-chemical properties
Solubility and solution behavior
CMC sodium is water soluble if DS is above a threshold (commonly >0.6).
Solubility increases with DS and decreases with increasing degree of crystallinity or residual lignin.
Solutions are typically clear to slightly opalescent colloidal solutions depending on Mw and particle dispersion history.
Viscosity and rheology
Viscosity of CMC solutions is a primary functional property.
It depends on concentration, Mw (intrinsic viscosity), DS, temperature, ionic strength and shear.
CMC solutions usually show pseudoplastic (shear-thinning) behavior and can produce wide ranges of viscosities at low concentrations (e.g., 0.5–2% w/w).
Viscosity is the most common grade spec (e.g., 400 cP, 1000 cP measured at specified concentration and temperature).
Degree of substitution (DS)
DS controls charge density, solubility and interactions.
Typical commercial DS range is ~0.6–0.95. DS also influences salt tolerance: higher DS improves solubility and salt/alcohol tolerance.
Thermal stability
CMC is a polysaccharide derivative with thermal decomposition typically commencing above 200–250°C.
Physical properties such as viscosity are affected by temperature and pH but CMC is stable for typical processing temperatures used in food and cosmetics.
Thermal degradation behavior is characterized by TGA/DTG.
Interaction with salts and pH
CMC is sensitive to multivalent cations (e.g., Ca²⁺, Al³⁺) which can reduce viscosity by charge shielding or by crosslinking (sometimes used intentionally to gel).
High ionic strength lowers electrostatic repulsion, lowering viscosity.
pH affects degree of ionization (carboxy groups remain mostly ionized over neutral pH ranges), but in strongly acidic conditions some protonation can occur, changing solubility and viscosity.
Analytical characterization and quality metrics
Essential analytical tests for CMC include:
Viscosity/intrinsic viscosity (Brookfield or capillary methods; specified concentration, temperature and spindle).
Degree of substitution (DS) — titrimetric or spectroscopic methods (back titration, ^1H NMR, FTIR correlation).
Molecular weight distribution — viscometry or GPC (if soluble in chosen solvent).
Moisture content — Karl Fischer or oven drying (affects flowability and dosing).
Residual salt (NaCl) and ash content — important for food/pharma grades.
pH of 1% solution — quality control metric.
Microbial limits — for food and pharma grades.
Heavy metals and elemental analysis — per regulatory specifications for sensitive applications.
Grades and specifications
Commercial grades are classified by:
Viscosity grade: low, medium, high (specified as viscosity at defined conditions).
Purity grade: industrial, technical, food-grade (≥99.5% for food high-purity), pharmaceutical/USP grades with stricter microbial and impurity limits.
Additional form factors: powdered, granulated, microgranules and aqueous solutions/slurries for direct use.
Functional mechanisms (how CMC works in formulations)
Thickening / viscosity control: hydrodynamic volume of hydrated polymer chains increases solution viscosity; shear thinning arises from alignment under flow.
Stabilization / emulsification: increases continuous phase viscosity, retarding droplet coalescence; also provides steric/electrostatic stabilization depending on interface interactions.
Film formation: on drying, CMC forms cohesive films used in coatings, tablet binders and paper coatings.
Water retention / moisture management: binds and holds water, useful in bakery, personal care and construction mortars.
Binding: used as binder in tablets and battery electrodes (CMC used as binder for anode/cathode slurries).
SAFETY INFORMATION ABOUT SODIUM CARBOXY METHYL CELLULOSE
First aid measures:
Description of first aid measures:
General advice:
Consult a physician.
Show this safety data sheet to the doctor in attendance.
Move out of dangerous area:
If inhaled:
If breathed in, move person into fresh air.
If not breathing, give artificial respiration.
Consult a physician.
In case of skin contact:
Take off contaminated clothing and shoes immediately.
Wash off with soap and plenty of water.
Consult a physician.
In case of eye contact:
Rinse thoroughly with plenty of water for at least 15 minutes and consult a physician.
Continue rinsing eyes during transport to hospital.
If swallowed:
Do NOT induce vomiting.
Never give anything by mouth to an unconscious person.
Rinse mouth with water.
Consult a physician.
Firefighting measures:
Extinguishing media:
Suitable extinguishing media:
Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
Special hazards arising from the substance or mixture
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas
Advice for firefighters:
Wear self-contained breathing apparatus for firefighting if necessary.
Accidental release measures:
Personal precautions, protective equipment and emergency procedures
Use personal protective equipment.
Avoid breathing vapours, mist or gas.
Evacuate personnel to safe areas.
Environmental precautions:
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Methods and materials for containment and cleaning up:
Soak up with inert absorbent material and dispose of as hazardous waste.
Keep in suitable, closed containers for disposal.
Handling and storage:
Precautions for safe handling:
Avoid inhalation of vapour or mist.
Conditions for safe storage, including any incompatibilities:
Keep container tightly closed in a dry and well-ventilated place.
Containers which are opened must be carefully resealed and kept upright to prevent leakage.
Storage class (TRGS 510): 8A: Combustible, corrosive hazardous materials
Exposure controls/personal protection:
Control parameters:
Components with workplace control parameters
Contains no substances with occupational exposure limit values.
Exposure controls:
Appropriate engineering controls:
Handle in accordance with good industrial hygiene and safety practice.
Wash hands before breaks and at the end of workday.
Personal protective equipment:
Eye/face protection:
Tightly fitting safety goggles.
Faceshield (8-inch minimum).
Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
Skin protection:
Handle with gloves.
Gloves must be inspected prior to use.
Use proper glove
removal technique (without touching glove's outer surface) to avoid skin contact with this product.
Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices.
Wash and dry hands.
Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
Splash contact
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
It should not be construed as offering an approval for any specific use scenario.
Body Protection:
Complete suit protecting against chemicals, The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
Respiratory protection:
Where risk assessment shows air-purifying respirators are appropriate use a fullface respirator with multi-purpose combination (US) or type ABEK (EN 14387) respirator cartridges as a backup to engineering controls.
If the respirator is the sole means of protection, use a full-face supplied air respirator.
Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
Control of environmental exposure
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Stability and reactivity:
Chemical stability:
Stable under recommended storage conditions.
Incompatible materials:
Strong oxidizing agents:
Hazardous decomposition products:
Hazardous decomposition products formed under fire conditions.
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas.
Disposal considerations:
Waste treatment methods:
Product:
Offer surplus and non-recyclable solutions to a licensed disposal company.
Contact a licensed professional waste disposal service to dispose of this material.
Contaminated packaging:
Dispose of as unused product
