Carboxymethyl cellulose (CMC) is a water-soluble cellulose derivative that is widely used in a variety of industries, including food, pharmaceuticals, and personal care. The degree of substitution (DS) is an important parameter that affects the properties of CMC. In this article, we will discuss the influence of DS on carboxymethyl cellulose quality.
First, it is important to understand what the degree of substitution is. The degree of substitution refers to the number of carboxymethyl groups per glucose unit in the cellulose chain. CMC is produced by reacting cellulose with sodium monochloroacetate and sodium hydroxide. During this reaction, the hydroxyl groups on the cellulose chain are replaced by carboxymethyl groups. The degree of substitution can be controlled by varying the reaction conditions, such as the concentration of sodium hydroxide and sodium monochloroacetate, the reaction time, and the temperature.
The DS of CMC affects its physical and chemical properties, such as its solubility, viscosity, and thermal stability. CMC with a low DS has a higher degree of crystallinity and is less water-soluble than CMC with a high DS. This is because the carboxymethyl groups in CMC with a low DS are located on the surface of the cellulose chain, which reduces its water-solubility. In contrast, CMC with a high DS has a more amorphous structure and is more water-soluble than CMC with a low DS.
The viscosity of CMC is also affected by the DS. CMC with a low DS has a lower viscosity than CMC with a high DS. This is because the carboxymethyl groups in CMC with a low DS are spaced further apart, which reduces the interaction between the cellulose chains and lowers the viscosity. In contrast, CMC with a high DS has a higher viscosity because the carboxymethyl groups are closer together, which increases the interaction between the cellulose chains and raises the viscosity.
In addition to its physical properties, the DS of CMC also affects its chemical properties. CMC with a low DS is less stable at high temperatures and pH values than CMC with a high DS. This is because the carboxymethyl groups in CMC with a low DS are more susceptible to hydrolysis and can break down under harsh conditions. In contrast, CMC with a high DS is more stable at high temperatures and pH values because the carboxymethyl groups are more tightly bound to the cellulose chain.