Hydroxyethyl Cellulose (HEC) is a water-soluble polymer compound obtained by chemical modification of natural cellulose. It is widely used in coatings, daily chemicals, building materials and other fields. Different types of HEC are mainly classified by parameters such as degree of substitution (DS), molar substitution (MS), viscosity, etc.

1. Classification by degree of substitution

The degree of substitution (DS) refers to the average number of hydroxyethyl groups on each glucose unit. Changes in DS will affect the solubility, viscosity and application areas of HEC.
Low degree of substitution HEC: DS is below 1.0. Low degree of substitution HEC has low solubility and is usually used in areas that require a certain degree of water resistance, such as building materials and certain coatings.
Medium degree of substitution HEC: DS is between 1.0 and 2.0. This type of HEC has good water solubility and high viscosity, and is often used in daily chemical products (such as detergents and cosmetics), coatings and emulsions.
High degree of substitution HEC: DS is above 2.0. This type of HEC has higher water solubility and is often used in applications that require high transparency and high viscosity, such as eye drops, thickeners in the food industry, etc.

2. Classification by molar substitution
Molar substitution (MS) refers to the average number of hydroxyethyl groups on each glucose unit, but includes multi-step reactions that occur during the substitution reaction. The higher the MS value, the better the water solubility and dissolution rate of the HEC are generally.
Low molar substitution HEC: MS is less than 1. This type of HEC has a slower dissolution rate and may require higher temperatures or long stirring times. It is suitable for applications that require delayed dissolution or controlled release.
Medium molar substitution HEC: MS is between 1 and 2. It has a moderate dissolution rate and is widely used in daily chemicals, coatings, and construction.
High molar substitution HEC: MS is greater than 2. It has a faster dissolution rate and excellent solubility, and is suitable for applications that require fast dissolution or transparent solutions, such as cosmetics and certain medical preparations.

3. Classification by viscosity
The viscosity of HEC is an important indicator of its fluidity in solution, usually based on the dilution (concentration) of the solution and the measurement conditions (such as shear rate).
Low viscosity HEC: The viscosity in 1% solution is less than 1000 mPa·s. Low viscosity HEC is suitable for use as a rheology control agent, dispersant and lubricant, and is widely used in daily chemical products, food industry, and certain pharmaceutical preparations.
Medium viscosity HEC: The viscosity in 1% solution is between 1000 and 4000 mPa·s. Medium viscosity HEC is widely used in coatings, adhesives, printing inks, and building materials industries, providing good thickening effects and rheology control.
High viscosity HEC: The viscosity in 1% solution is higher than 4000 mPa·s. High viscosity HEC is mainly used as a thickener and stabilizer, suitable for fields requiring high viscosity and high transparency, such as high-end coatings, cosmetics, and certain special industrial applications.

4. Classification by product form
HEC can also be classified according to its physical form, which often affects its application and handling.
Powdered HEC: The most common form, easy to transport and store. Used in most industrial and daily chemical applications, it needs to be mixed into water to form a solution.
Granular HEC: Granular HEC is easier to handle and dissolve than powdered HEC, reducing dust problems and suitable for large-scale industrial production.
Solution-type HEC: In some high-end applications, HEC may be provided directly in solution form, which is convenient for direct use and reduces dissolution time, such as in some cosmetics and pharmaceutical products.

5. Special functional HEC
There are also some HECs that have been further chemically modified or physically treated to meet the needs of specific applications.
Crosslinked HEC: HEC’s water resistance and mechanical properties are improved by chemical crosslinking, and it is suitable for occasions requiring high strength and durability.
Modified HEC: Further modification (such as carboxymethylation, phosphorylation, etc.) is made on the basis of HEC to give it more functions, such as improved antibacterial properties, heat resistance or adhesion.
Mixed HEC: Compounded with other thickeners or functional materials to enhance its comprehensive performance, such as the application of composite thickeners in coatings.

As an important water-soluble polymer material, different types of hydroxyethyl cellulose (HEC) adapt to different application requirements through changes in degree of substitution, molar substitution, viscosity and physical form. Understanding these classifications helps to select suitable HEC products in practical applications to obtain the best performance and effect. Whether in daily chemicals, building materials, coatings or medicine, HEC is widely used for its good thickening, moisturizing and film-forming properties.