Performance Characteristics and Functions of Carboxymethyl Cellulose (CMC)

Carboxymethyl cellulose (CMC) is an anionic cellulose ether made from natural cellulose via an etherification reaction. It is currently one of the most widely used water-soluble polymer materials worldwide, boasting excellent thickening, emulsification, stabilization, water retention, and film-forming properties. It plays an important role in industries such as food, pharmaceuticals, daily chemicals, ceramics, oil drilling, and construction.

1. Performance Characteristics of CMC

1.1. Excellent Water Solubility
CMC dissolves rapidly in cold or hot water, forming transparent or translucent viscous solutions. Its solubility is closely related to the degree of substitution (DS), with higher DS indicating better solubility. Compared to other natural polymers, CMC exhibits superior dispersibility and solution stability, with solutions less prone to stratification or precipitation.

1.2. Outstanding Thickening and Rheological Properties
Aqueous CMC solutions exhibit excellent thickening properties, effectively increasing system viscosity, and exhibit shear-thinning properties characteristic of pseudoplastic fluids. This property significantly improves fluidity and application/use feel in applications such as coatings, mortars, food sauces, and detergents.

1.3. Excellent Water Retention and Film-Forming Properties
CMC molecules contain numerous carboxymethyl and hydroxyl groups, which strongly adsorb water molecules and form a uniform hydrated film, resulting in excellent water retention. The resulting film, after drying, is transparent, flexible, and possesses considerable strength. It is widely used in food coatings, pharmaceutical tablet coatings, and as a ceramic binder.

1.4. Strong Chemical Stability and Safety and Environmental Protection
CMC is a nonionic or weakly anionic polymer that is relatively stable to heat, light, and oxygen, and exhibits excellent salt, acid, and alkali resistance (stable within a pH range of 5–9). Derived from natural cellulose, it is biodegradable, non-toxic, and odorless, meeting environmental requirements.

1.5. Good Compatibility and Synergistic Effects
CMC is compatible with a variety of organic and inorganic ingredients, such as carbohydrates, proteins, surfactants, other colloids, and polymers, often creating synergistic effects in compound systems. For example, when used in combination with hydroxypropyl methylcellulose (HPMC) or PVA, it can improve coating stability and adhesion strength.

2. Functions of CMC

2.1. Thickening and Rheology Modifier
In foods, daily chemicals, and coatings, CMC primarily thickens and improves rheological properties. For example, it provides a suitable consistency and smooth mouthfeel in beverages, jams, and sauces; in laundry detergents and shampoos, it prevents component separation and improves product wall adhesion.

2.2. Stabilizing and Emulsifying Effects
CMC forms a stable three-dimensional network structure in the system, preventing particle sedimentation or separation. In emulsion systems, CMC can adsorb onto the surface of the dispersed phase, enhancing interfacial film strength and thus improving emulsion stability. It is widely used in emulsion paints, milk beverages, and emulsified batters.

2.3. Water Retention and Anti-Settling Effects
CMC has excellent water absorption and moisture retention capabilities, preventing water loss in the system. In building mortars and ceramic blanks, CMC prevents rapid evaporation, improving workability and bonding strength. In food dough, it maintains softness and ductility.

2.4. Film-Forming and Adhesive Properties
After drying, CMC forms a flexible, transparent film with excellent adhesive properties. In the papermaking industry, it is used for surface sizing, improving paper smoothness and printability. It is also commonly used as a film-forming agent and binder in ceramics, pharmaceutical tablets, and textile sizing.

2.5. Suspension and Controlled-Release Functions
In oil drilling fluids, CMC increases mud viscosity, enhances sand-carrying capacity, and stabilizes the suspension system. In pharmaceutical formulations, it can serve as a sustained-release matrix material to regulate drug release rate.

3. Application Prospects

With the development of green chemistry and renewable materials, CMC, due to its natural origin, safety, non-toxicity, and biodegradability, will find wider application in food safety, pharmaceutical environmental protection, new energy, and polymer composites. In the future, functionalized, modified, and compounded CMC products will become important research and industrial upgrading directions.