Technical information

GRINDSTED® Cellulose gum (CMC) is a linear anionic polymer based on cellulose.

It functionality in the final application depends on its chemical properties:

• Molecular weight: length of the cellulose used as raw material. The molecular weight mainly defines the final viscosity of the GRINDSTED® Cellulose gum (CMC) solution.
• Degree of substitution (DS): Number of carboxymethyl per glucose unit. May vary from 0.4 to 1.5. The DS defines the hydrophilic properties of the GRINDSTED® Cellulose gum (CMC). The higher the DS, the higher the water solubility, pH resistance, salt compatibility etc.
• Purity: based on dry powder.
  

Absorbtion properties
As a result of its hydrophilic properties, GRINDSTED® Cellulose gum (CMC) can bind water and develop absorption properties. The absorption capacity will mainly depend on the molecular weight and DS.

This property is used in a number of applications such as food (bakery) pharmaceuticals (woundcare) and personal care (female hygiene).
GRINDSTED® Cellulose gum (CMC) with a DS = 0.4 can absorb about 20% moisture when the relative humidity degree is 80%.

Chart 1: CMC absorbing quantity under different relative humidity degrees.

Solubility
Water is the best solvent for GRINDSTED® Cellulose gum (CMC). Solubility in water is dependant on the DS value and the molecular weight. A low molecular weight and a high DS result in high solubility. GRINDSTED® Cellulose gum (CMC) is also soluble in most aqueous mixes such as alcohol/water, glycerine/water etc. When other solutes such as salts are added, it is recommended to dissolve the cellulose gum first.

When GRINDSTED® Cellulose gum (CMC) is added directly to the water, it is recommended to add it under strong agitation (in the vortex) to avoid any lump formation. CG/CMC can also be dry-blended with other ingredients like sugar, flour etc. Another way to efficiently dissolve the GRINDSTED® Cellulose gum (CMC) is to disperse it in a non solvent carrier (oil, glycerine, sugar syrup etc.) and then to dilute this suspension in pure water.

Chart 2: The effect of CMC solution under different temperatures.

Rheological properties
GRINDSTED® Cellulose gum (CMC) solutions exhibit a non-Newtonian behaviour. The viscosity rapidly decreases when high shear is applied. This behaviour facilitates the handling of GRINDSTED® Cellulose gum (CMC) during the process, with no effect on the viscosity of the finished product.

The viscosity of GRINDSTED® Cellulose gum (CMC) solution increases rapidly with concentration. The viscosity is usually multiplied by 10 when the concentration is double (i.e., a 1% solution with a viscosity of 100cp will show a viscosity of 1000cp when the concentration reaches 2%).

Under normal conditions, the viscosity of GRINDSTED® Cellulose gum (CMC) solutions drop as the temperature rises – see Chart 2. The same behaviour occurs when the pH decreases. When the pH is higher than 10, the viscosity will increase slightly (see Chart 4).

Certain viscosity types can also develop a thixotropic behaviour. This is one of the key parameters of our GRINDSTED® Cellulose gum (CMC) in toothpaste applications. In addition, the process used by Danisco gives an evenly homogeneous substitution, which exhibits excellent performance under acidic and high ionic conditions and shows smooth and fine characteristics.

Chart 3 shows that the viscosity of GRINDSTED® Cellulose gum (CMC) in glycerin/H2O is greater than in water alone.

Chart 3: The effect of glycerin on the viscosity of CMC water solution.

Chart 4: The stability of CMC solution under different acidic conditions.