The NaCMC is usually known as cellulose gum. It is ananionic water-soluble polymeric polyelectrolyte. Manufacturing of cellulosederivatives is complete by treating the free hydroxyl groups in the anhydroglucose units (AGU) with differentchemical substitution groups. The introduction of the substituent concerns theinter- and intramolecular hydrogen bonds in cellulose, which leads to the liberation of the hydrophilic character of the numeroushydroxyl groups and limit the chains to closely associate 14.Though,substitution with alkyl groups may reducethe number of free hydroxyl groups.
Physical and chemical properties of carboxymethylcellulose are mainly determined by the degree of substitution, distribution, and degree of polymerization.Among these properties, the degree ofsubstitution has the utmost influence on the solubility, shearing stability andrheological behavior of carboxymethyl cellulose solution and its stabilityagainst temperature and low molecular additives. The degree of substitution represents the number of thecarboxymethyl 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 ofsubstitution is being 3.0 15.Properties of CMCThe properties of carboxymethylcellulose depend on the degree of substitution and the length of the cellulosechains. The degree of substitution may vary in commercial products from 0.4 to1.5.
Carboxymethyl cellulose is non-toxic and becomes very viscous whencombined with water. It is white to off-whitepowder, soluble in aqueous solution, high viscosity, it is soluble at up to 50mg/ml concentration but heat may be required. It is typically used atconcentrations less than 20 mg/ml. Under normal conditions, the effect oftemperature on solutions of carboxymethyl cellulose is reversible. Minor variationin temperature has no permanent effect on viscosity.
However, long periods ofheating CMC solutions at high temperatures, such as autoclaving, will degradeCMC and permanently reduce viscosity 12.Characterization of the carboxymethylcelluloseSeveralmethods were established in order to characterize the raw materials as well asthe prepared sodium salt of carboxymethylcellulose (NaCMC).