Sodium carboxymethyl cellulose (CMC), also known as carboxymethyl cellulose. It is a high-polymer cellulose ether prepared by chemically modifying natural cellulose, and its structure is mainly composed of D-glucose units linked by β_(14) glycosidic bonds.
CMC is a white or milky white fibrous powder or granules with a density of 0.5g/cm3, almost tasteless, odorless and hygroscopic.
Carboxymethyl cellulose is easy to disperse, forms a transparent colloidal solution in water, and is insoluble in organic solvents such as ethanol.
When pH>10, the pH value of 1% aqueous solution is 6.5≤8.5.
The main reaction is as follows: the natural cellulose is first alkalized with NaOH, then chloroacetic acid is added, and the hydrogen on the hydroxyl group on the glucose unit reacts with the carboxymethyl group in the chloroacetic acid.
It can be seen from the structure that there are three hydroxyl groups on each glucose unit, namely C2, C3 and C6 hydroxyl groups, and the substitution degree of hydrogen on the hydroxyl group of glucose unit is represented by physical and chemical indicators.
If the hydrogens on the three hydroxyl groups on each unit are replaced by carboxymethyl groups, then the degree of substitution is defined as 7-8, with a maximum degree of substitution of 1.0 (food grade can only achieve this degree). The degree of substitution of CMC directly affects the solubility, emulsification, thickening, stability, acid resistance and salt resistance of CMC.
When using CMC products, we should fully understand the main index parameters, such as stability, viscosity, acid resistance, viscosity, etc.
Of course, different applications use different carboxymethyl cellulose, because there are many types of viscosity acting on carboxymethyl cellulose, and the physical and chemical indicators are also different. Knowing these, you can know how to choose the right product.