Methylcellulose (MC) is a common chemically synthesized polymer material, a modified cellulose ether obtained by methylating natural cellulose. Due to its special physical and chemical properties, it is widely used in construction, food, medicine, cosmetics, paper and coatings.
1. Classification by degree of substitution
The degree of substitution (DS) refers to the average value of hydroxyl groups substituted by methyl groups on each glucose unit in methylcellulose. There are 3 hydroxyl groups on each glucose ring of the cellulose molecule that can be replaced by methyl groups. Therefore, the degree of substitution of methylcellulose can vary from 0 to 3. According to the degree of substitution, methylcellulose can be divided into two categories: high degree of substitution and low degree of substitution.
High degree of substitution methylcellulose (DS > 1.5): This type of product has a high degree of methyl substitution, so it is more hydrophobic, has lower solubility and good water resistance. It is often used in building materials, coatings and other occasions that require a certain degree of hydrophobicity.
Low degree of substitution methylcellulose (DS < 1.5): Due to less methyl substitution, this type of product is more hydrophilic, has better solubility and can be dissolved in cold water. Low-substituted methylcellulose is widely used in the food and pharmaceutical industries as a thickener, emulsifier and stabilizer.
2. Classification by use
According to the use of methylcellulose in different fields, it can be divided into two categories: industrial methylcellulose and food and pharmaceutical methylcellulose.
Industrial methylcellulose: Mainly used in the construction, coatings, papermaking, ceramics and other industries as a thickener, adhesive, film former, water retaining agent, etc. In the construction industry, methylcellulose is used in cement and gypsum products to improve construction performance and durability; in the coatings industry, methylcellulose can increase the stability and dispersibility of coatings.
Food and pharmaceutical methylcellulose: Due to its non-toxic and harmless properties, methylcellulose is used as an additive in food and medicine. In food, methylcellulose is a common thickener and emulsifier that can stabilize the food structure and prevent stratification or separation; in the pharmaceutical field, methylcellulose can be used as a capsule shell, a drug carrier, and also has the function of sustained-release drugs. Its edibility and safety make methylcellulose very popular in these two fields.
3. Classification by solubility
Methylcellulose is mainly divided into two categories in terms of solubility: cold water soluble type and organic solvent soluble type.
Cold water soluble methylcellulose: This type of methylcellulose can be dissolved in cold water to form a transparent, viscous solution after dissolution. It is often used in the food and pharmaceutical industries as a thickener or film former. The solubility of this type of methylcellulose decreases with increasing temperature, so this feature can be used for construction control when used in the construction industry.
Organic solvent soluble methylcellulose: This type of methylcellulose can be dissolved in organic solvents and is often used in paints, coatings and other industrial fields that require organic phase media. Due to its good film-forming properties and chemical resistance, it is suitable for use under harsh industrial conditions.
4. Classification by molecular weight (viscosity)
The molecular weight of methylcellulose has a significant effect on its physical properties, especially the viscosity performance in the solution. According to the molecular weight, methylcellulose can be divided into low viscosity type and high viscosity type.
Low viscosity methylcellulose: The molecular weight is relatively small and the solution viscosity is low. It is often used in food, medicine and cosmetics, mainly for emulsification, suspension and thickening. Low-viscosity methylcellulose can maintain good fluidity and uniformity, and is suitable for applications that require low-viscosity solutions.
High-viscosity methylcellulose: It has a large molecular weight and forms a high-viscosity solution after dissolution. It is often used in building materials, coatings and industrial adhesives. High-viscosity methylcellulose can effectively increase the mechanical strength, wear resistance and adhesion of the solution, so it is widely used in materials that require high strength and high wear resistance.
5. Classification by degree of chemical modification
Methylcellulose is a chemically modified cellulose derivative. According to the modification method and degree, it can be divided into single methyl cellulose and composite modified cellulose.
Single methyl cellulose: refers to cellulose ethers that are only methyl-substituted. This type of product has relatively stable physical and chemical properties, and its solubility, thickening and film-forming properties are relatively good.
Composite modified cellulose: In addition to methylation, it is further chemically treated, such as hydroxypropylation, ethylation, etc., to form a composite modified product. For example, hydroxypropyl methylcellulose (HPMC) and carboxymethyl cellulose (CMC). These composite modified celluloses usually have better water solubility, heat resistance and stability, and can adapt to a wider range of industrial needs.
6. Classification by application industry
The wide application of methylcellulose allows it to be classified according to its application characteristics in different industries.
Construction industry methylcellulose: Mainly used in cement-based and gypsum-based materials as a water retainer and thickener. It can improve the operability of building materials, prevent early water loss, and increase the mechanical strength of finished products.
Food industry methylcellulose: As an emulsifier, thickener and stabilizer in food processing. It can prevent water loss, improve the taste and structure of food, and increase the shelf life of food.
Pharmaceutical industry methylcellulose: As a tablet binder or a sustained-release material for drugs. Methylcellulose can also be used in the preparation of gastrointestinal drugs as a safe and effective drug carrier.
Cosmetic industry methylcellulose: In skin care products and cosmetics, methylcellulose is used as a thickener, emulsifier and moisturizer to help products form a delicate and smooth texture while prolonging the moisturizing effect.
In summary, there are many ways to classify methylcellulose, which can be classified according to its chemical structure characteristics, or according to its application fields and solubility properties. These different classification methods help us better understand the characteristics and functions of methylcellulose, and also provide a theoretical basis for its application in different fields.
Post time: Oct-23-2024