The NaCMC is usually known as cellulose gum. It is an
anionic water-soluble polymeric polyelectrolyte. Manufacturing of cellulose
derivatives is complete by treating the free hydroxyl groups in the anhydroglucose units (AGU) with different
chemical substitution groups. The introduction of the substituent concerns the
inter and intramolecular hydrogen bonds in cellulose, which leads to the liberation of the hydrophilic character of the numerous
hydroxyl groups and limit the chains to closely associate 14.Though,
substitution with alkyl groups may reduce
the number of free hydroxyl groups. Physical and chemical properties of carboxymethyl
cellulose are mainly determined by the degree of substitution, distribution, and degree of polymerization.
Among these properties, the degree of
substitution has the utmost influence on the solubility, shearing stability and
rheological behavior of carboxymethyl cellulose solution and its stability
against temperature and low molecular additives. The degree of substitution represents the number of the
carboxymethyl groups in the molecular unit of the anhydroglucose units. In principle,
all hydroxyl groups (HO-2, HO-3, and HO-6) in the anhydroglucose unit can be substituted, and the maximum degree of
substitution is being 3.0 15.
Properties of CMC
The properties of carboxymethyl
cellulose depend on the degree of substitution and the length of the cellulose
chains. The degree of substitution may vary in commercial products from 0.4 to
1.5. Carboxymethyl cellulose is non-toxic and becomes very viscous when
combined with water. It is white to off-white
powder, soluble in aqueous solution, high viscosity, it is soluble at up to 50
mg/ml concentration but heat may be required. It is typically used at
concentrations less than 20 mg/ml. Under normal conditions, the effect of
temperature on solutions of carboxymethyl cellulose is reversible. Minor variation
in temperature has no permanent effect on viscosity. However, long periods of
heating CMC solutions at high temperatures, such as autoclaving, will degrade
CMC and permanently reduce viscosity 12.
Characterization of the carboxymethylcellulose
methods were established in order to characterize the raw materials as well as
the prepared sodium salt of carboxymethylcellulose (NaCMC).