Carboxymethyl cellulose (CMC) and hydroxyethyl cellulose (HEC) are two common cellulose derivatives, which are widely used in food, medicine, cosmetics, building materials and other fields. Although they are both derived from natural cellulose and obtained by chemical modification, there are obvious differences in chemical structure, physicochemical properties, application fields and functional effects.
1. Chemical structure
The main structural feature of carboxymethyl cellulose (CMC) is that the hydroxyl groups on the cellulose molecules are replaced by carboxymethyl (-CH2COOH) groups. This chemical modification makes CMC extremely water-soluble, especially in water to form a viscous colloidal solution. The viscosity of its solution is closely related to its degree of substitution (i.e. the degree of carboxymethyl substitution).
Hydroxyethyl cellulose (HEC) is formed by replacing the hydroxyl groups in cellulose with hydroxyethyl (-CH2CH2OH). The hydroxyethyl group in the HEC molecule increases the water solubility and hydrophilicity of cellulose, and can form a gel under certain conditions. This structure enables HEC to show good thickening, suspension and stabilization effects in aqueous solution.
2. Physical and chemical properties
Water solubility:
CMC can be completely dissolved in both cold and hot water to form a transparent or translucent colloidal solution. Its solution has high viscosity, and the viscosity changes with temperature and pH value. HEC can also be dissolved in cold and hot water, but compared with CMC, its dissolution rate is slower and it takes longer to form a uniform solution. The solution viscosity of HEC is relatively low, but it has better salt resistance and stability.
Viscosity adjustment:
The viscosity of CMC is easily affected by pH value. It is usually higher under neutral or alkaline conditions, but the viscosity will be significantly reduced under strong acidic conditions. The viscosity of HEC is less affected by pH value, has a wider range of pH stability, and is suitable for applications under various acidic and alkaline conditions.
Salt resistance:
CMC is highly sensitive to salt, and the presence of salt will significantly reduce the viscosity of its solution. HEC, on the other hand, exhibits strong salt resistance and can still maintain a good thickening effect in a high-salt environment. Therefore, HEC has obvious advantages in systems that require the use of salts.
3. Application areas
Food industry:
CMC is widely used in the food industry as a thickener, stabilizer and emulsifier. For example, in products such as ice cream, beverages, jams, and sauces, CMC can improve the taste and stability of the product. HEC is relatively rarely used in the food industry and is mainly used in some products with special requirements, such as low-calorie foods and special nutritional supplements.
Medicine and cosmetics:
CMC is often used to prepare sustained-release tablets of drugs, eye liquids, etc., because of its good biocompatibility and safety. HEC is widely used in cosmetics such as lotions, creams and shampoos due to its excellent film-forming and moisturizing properties, which can provide a good feel and moisturizing effect.
Building materials:
In building materials, both CMC and HEC can be used as thickeners and water retainers, especially in cement and gypsum-based materials. HEC is more widely used in building materials due to its good salt resistance and stability, which can improve the construction performance and durability of materials.
Oil extraction:
In oil extraction, CMC, as an additive for drilling fluid, can effectively control the viscosity and water loss of mud. HEC, due to its superior salt resistance and thickening properties, has become an important component in oilfield chemicals, used in drilling fluid and fracturing fluid to improve operating efficiency and economic benefits.
4. Environmental protection and biodegradability
Both CMC and HEC are derived from natural cellulose and have good biodegradability and environmental friendliness. In the natural environment, they can be degraded by microorganisms to produce harmless substances such as carbon dioxide and water, reducing pollution to the environment. In addition, because they are non-toxic and harmless, they are widely used in products that come into direct contact with the human body, such as food, medicine and cosmetics.
Although carboxymethyl cellulose (CMC) and hydroxyethyl cellulose (HEC) are both derivatives of cellulose, they have significant differences in chemical structure, physicochemical properties, application fields and functional effects. CMC is widely used in food, medicine, oil extraction and other fields due to its high viscosity and susceptibility to environmental influences. HEC, however, is more widely used in cosmetics, building materials, etc. due to its excellent salt resistance, stability and film-forming properties. When choosing to use it, it is necessary to select the most suitable cellulose derivative according to the specific application scenario and needs to achieve the best use effect.
Post time: Aug-21-2024