Core Properties of Sodium Carboxymethyl Cellulose (CMC)
Sodium carboxymethyl cellulose is an important water-soluble polymer with a wide range of properties and applications. Its core properties are as follows:
1. Physicochemical Properties
Appearance: White/slightly yellow powder, granules, or fibers, odorless and tasteless, with good fluidity.
Solubility: Easily soluble in water to form a transparent, viscous liquid (swelling first, then dissolving), insoluble in organic solvents.
Structure: Modified cellulose with negatively charged carboxymethyl groups, resulting in hydrophilic and electrolyte properties.
2. Solution-Related Properties
Thickening: A small amount can significantly increase viscosity, and viscosity is positively correlated with molecular weight, degree of substitution, and concentration.
Film-Forming Properties: Upon drying, aqueous solutions form tough, transparent films with moderate barrier properties.
pH Stability: Stable between pH 6-9, readily precipitates in strong acids (pH < 3), and exhibits a slight decrease in viscosity in strong bases.
3. Rheological Properties
It is a pseudoplastic fluid with shear-thinning properties: viscosity decreases under external force (facilitating processing) and recovers after the force is removed (maintaining system stability).
4. Thermal Stability
Dry State: Stable below 100°C, but degrades, discolors, and exhibits performance degradation above 200°C.
Aqueous Solution: Viscosity decreases with increasing temperature, partially recovering with cooling. However, prolonged high temperature causes molecular chain breakage and irreversible viscosity loss.
5. Biocompatibility and Safety
Non-toxic: Approved as a food additive (E466) and pharmaceutical excipient, it meets safety standards.
Environmentally Friendly: Microbially degradable into carbon dioxide and water, making it environmentally friendly.
6. Functional Properties
Adhesion: Can be used as a binder in applications such as battery electrodes and papermaking, firmly bonding particles.
Suspension and Stability: Prevents solid particles from settling, maintains the stability of emulsions/emulsions, and prevents oil-water separation.
