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Cellulose derivatives have long been used to modify rheology and surface properties. Carboxymethylation of cellulose—introducing carboxymethyl (-CH₂COO⁻) groups onto the cellulose backbone—was developed in the first half of the 20th century and commercialized broadly for detergents, foodstuffs and industrial uses.
The sodium salt form (CMC-Na) is preferred for its water solubility and stability.
Modern industrial production and tailored grades (wide viscosity/DS ranges) allow application-specific selection.
CAS 9004-32-4.
Synonyms: sodium carboxymethyl cellulose; sodium carboxymethylcellulose; cellulose, carboxymethyl ether, sodium salt; sodium cellulose glycolate; cellulose gum; Cellulose, carboxymethyl ether
Chemical identity and structure
Basic chemistry
Backbone: Cellulose — linear β(1→4)-linked D-glucopyranose repeating units.
Modification: Some hydroxyl groups on the anhydroglucose units (AGUs) are etherified with carboxymethyl groups (–CH₂–COO⁻) to yield carboxymethylcellulose.
The sodium salt form counterbalances the anionic carboxylates.
The substitution may occur at C2, C3 and/or C6 hydroxyls.
Degree of substitution (DS)
DS definition: average number of substituted hydroxyls per AGU (maximum theoretical DS = 3). Typical commercial CMC DS ranges from ~0.4 to ~1.2 depending on grade.
DS strongly influences solubility, charge density and interaction with ions. Higher DS increases anionic charge and water solubility.
Molecular weight / viscosity grade
CMC is a polymer; molecular weight (and distribution) varies by feedstock and processing. Manufacturers grade CMC by solution viscosity at a defined concentration (e.g., Brookfield viscosity at 1% or 2% w/w), giving “low”, “medium”, “high” viscosity grades.
Mw typically ranges from tens of thousands to several million g·mol⁻¹ depending on grade.
Viscosity correlates with chain length and hydrodynamic volume.
Production & manufacturing routes
Raw materials
Cellulosic feedstocks: wood pulp (softwood or hardwood), cotton linters, agricultural residues (e.g., cornstalks) after bleaching/purification.
Typical industrial synthesis (etherification route)
Alkalization: Cellulose is slurried in an alkaline medium (sodium hydroxide, NaOH). Alkali swells cellulose and converts hydroxyls to alkoxide forms that are nucleophilic.
Etherification: Monochloroacetic acid (MCAA, ClCH₂COOH) or its sodium salt (sodium monochloroacetate, SMCA) is added.
The alkoxide attacks the haloacetate, producing carboxymethyl ether linkages and releasing chloride as NaCl.
Reaction conditions (temperature, solvent, reagent ratios, presence of alcohol or isopropanol, water content) determine DS, substitution pattern and by-products.
Process variants and purification
Technical CMC vs. purified grades: Technical grades (e.g., for detergents, paper) are often used directly after reaction and neutralization; they contain salts (NaCl, sodium glycolate) and residuals. Food and pharmaceutical grades undergo washing, dialysis, or ion-exchange and demineralization to remove salts and lower ash content.
Controlled etherification and subsequent purification yield consistent viscosity and low impurities required for sensitive applications.
Process control parameters
NaOH : MCAA : Cellulose ratio — tunes DS and amount of side reactions.
Solvent system: aqueous vs. water/alcohol mixtures — affects dissolution/swelling and reaction kinetics and dissolution behavior of the final powder.
Patents describe use of ethanol/isopropanol mixtures for improved dissolution properties.
Physicochemical properties
Physical appearance
White to off-white, odorless powder; highly hygroscopic.
Soluble in water to give clear to opalescent viscous solutions depending on grade.
Solubility
Soluble in cold and hot water; insoluble in common organic solvents (methanol, ethanol, acetone, chloroform).
Solubility increases with DS and decreases with crosslinking or high crystallinity. Hydration behavior (rate of dispersion and dissolution) depends on particle size, viscosity grade and salt content.
Rheology and solution behavior
CMC solutions show non-Newtonian shear thinning (pseudoplastic) behavior and can exhibit thixotropy depending on concentration and molecular weight.
Viscosity is highly dependent on concentration, DS, ionic strength and temperature.
Presence of multivalent cations (Ca²⁺, Al³⁺) screens anionic charges and can reduce viscosity or promote gelation/crosslinking.
Thermal stability
As a polymeric cellulose derivative, thermal decomposition occurs at elevated temperatures (generally >200 °C depending on moisture and grade).
CMC is stable under normal processing temperatures used for food and many polymer processes but will degrade above thermal decomposition thresholds.
Analytical characterization and quality control
Key quality attributes
Viscosity (solution): Brookfield or other rotational viscometers; commonly reported at defined % w/w and temperature.
Degree of substitution (DS): measured by titration of carboxyl groups, conductometric titration, or instrumental methods (¹H / ¹³C NMR integration).
Molecular weight / Mw distribution: GPC/SEC (size exclusion chromatography) with appropriate detectors (multi-angle light scattering for absolute Mw).
Ash (inorganic residue): indicates salt content (NaCl, Na₂CO₃) — important for food/pharma grades.
Moisture content: Karl Fischer or loss on drying.
pH of aqueous solution: quality indicator.
FTIR: confirms carboxylate functionality (C=O stretching, COO⁻ bands) and ether linkages.
Typical test methods
Standard pharmacopeial and industry methods (e.g., USP/NF, EP monographs for cellulose derivatives where applicable) describe viscosity procedures, ash limits and identity tests. Manufacturers publish certificates of analysis (CoA) listing viscosity, DS, pH, moisture and impurities
SAFETY INFORMATION ABOUT CARBOXYMETHYLCELLULOSE, SODIUM SALT
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
