Carboxymethyl Cellulose (CMC) and methyl cellulose (MC) are two cellulose derivatives widely used in many industries. Although they are both derived from natural cellulose, due to different chemical modification processes, CMC and MC have significant differences in chemical structure, physical and chemical properties, and application fields.
1. Source and basic overview
Carboxymethylcellulose (CMC) is prepared by reacting natural cellulose with chloroacetic acid after alkali treatment. It is an anionic water-soluble cellulose derivative. CMC usually exists in the form of sodium salt, so it is also called Sodium Carboxymethyl Cellulose (Na-CMC). Due to its good solubility and viscosity adjustment function, CMC is widely used in food, pharmaceutical, oil drilling, textile and paper industries.
Methylcellulose (MC) is prepared by methylating cellulose with methyl chloride (or other methylating reagents). It is a non-ionic cellulose derivative. MC has thermal gel properties, the solution solidifies when heated and dissolves when cooled. Due to its unique properties, MC is widely used in building materials, pharmaceutical preparations, coatings, food and other industries.
2. Chemical structure
The basic structure of CMC is the introduction of a carboxymethyl group (–CH2COOH) on the glucose unit of the β-1,4-glucosidic bond of cellulose. This carboxyl group makes it anionic. The molecular structure of CMC has a large number of sodium carboxylate groups. These groups are easily dissociated in water, making the CMC molecules negatively charged, thus giving it good water solubility and thickening properties.
The molecular structure of MC is the introduction of methoxy groups (–OCH3) into the cellulose molecules, and these methoxy groups replace part of the hydroxyl groups in the cellulose molecules. There are no ionized groups in the MC structure, so it is non-ionic, meaning it does not dissociate or become charged in solution. Its unique thermal gel properties are caused by the presence of these methoxy groups.
3. Solubility and physical properties
CMC has good solubility in water and can quickly dissolve in cold water to form a transparent viscous liquid. Since it is an anionic polymer, the solubility of CMC is affected by the ionic strength and pH value of water. In high-salt environments or strong acid conditions, the solubility and stability of CMC will decrease. In addition, the viscosity of CMC is relatively stable at different temperatures.
The solubility of MC in water depends on temperature. It can be dissolved in cold water but will form a gel when heated. This thermal gel property enables MC to play special functions in the food industry and building materials. The viscosity of MC decreases as the temperature increases, and it has good resistance to enzymatic degradation and stability.
4. Viscosity characteristics
The viscosity of CMC is one of its most important physical properties. The viscosity is closely related to its molecular weight and degree of substitution. The viscosity of CMC solution has good adjustability, usually producing higher viscosity at low concentration (1%-2%), so it is often used as a thickener, stabilizer and suspending agent.
The viscosity of MC is also related to its molecular weight and degree of substitution. MC with different degrees of substitution has different viscosity characteristics. MC also has a good thickening effect in the solution, but when heated to a certain temperature, the MC solution will gel. This gelling property is widely used in the construction industry (such as gypsum, cement) and food processing ( Such as thickening, film formation, etc.).
5. Application areas
CMC is commonly used as thickener, emulsifier, stabilizer, and suspending agent in the food industry. For example, in ice cream, yogurt and fruit drinks, CMC can effectively prevent ingredient separation and improve the taste and stability of the product. In the petroleum industry, CMC is used as a mud treatment agent to help control the fluidity and fluid loss of drilling fluids. In addition, CMC is also used for pulp modification in the paper industry and as sizing agent in the textile industry.
MC is widely used in the construction industry, especially in dry mortars, tile adhesives and putty powders. As a thickening agent and water retaining agent, MC can improve construction performance and bonding strength. In the pharmaceutical industry, MC is used as tablet binders, sustained-release materials and capsule wall materials. Its thermogelling properties enable controlled release in certain formulations. In addition, MC is also used in the food industry as a thickener, stabilizer and emulsifier for food, such as sauces, fillings, breads, etc.
6. Safety and biodegradability
CMC is considered a safe food additive. Extensive toxicological studies have shown that CMC is harmless to the human body at the recommended dosage. Since CMC is a derivative based on natural cellulose and has good biodegradability, it is relatively friendly in the environment and can be degraded by microorganisms.
MC is also considered a safe additive and is widely used in medicines, foods and cosmetics. Its non-ionic nature makes it highly stable in vivo and in vitro. Although MC is not as biodegradable as CMC, it is also able to be degraded by microorganisms under specific conditions.
Although carboxymethyl cellulose and methyl cellulose are both derived from natural cellulose, they have different characteristics in practical applications due to their different chemical structures, physical properties and application fields. CMC is widely used in the food, pharmaceutical and industrial fields due to its good water solubility, thickening and suspension properties, while MC occupies an important position in the construction, pharmaceutical and food industries due to its thermal gel properties and stability. Both have unique applications in modern industry, and both are green and environmentally friendly materials.