Properties and Uses of Hydroxyethyl Cellulose (HEC): Professional Discussion

Hydroxyethyl Cellulose (HEC) is a nonionic water-soluble polymer obtained by etherification modification of natural cellulose. Due to its unique physical and chemical properties, HEC has been widely used in many industrial fields. This article will systematically discuss the basic properties, preparation process and application of HEC in various industries, aiming to provide a reference for technical research and practical application in related fields.

### 1. Basic properties of hydroxyethyl cellulose

#### 1.1 Molecular structure and physical properties

The molecular structure of HEC is based on the β-D-pyranose glucopyranose of natural cellulose, which is formed by replacing part of the hydroxyl groups with ethoxy groups. The molecular structure of HEC contains a large number of hydrophilic groups, which makes it well soluble in water. The molecular weight and degree of substitution of HEC (i.e., the average number of hydroxyethyl substituents on each glucose unit) are the key parameters affecting its performance. With the increase of degree of substitution, the water solubility and solution viscosity of HEC increase, but its gelation temperature decreases.

#### 1.2 Solubility and Solution Properties

HEC can be dissolved in both cold and hot water to form a transparent or translucent viscous liquid. The solubility of HEC is affected by molecular weight and degree of substitution. HEC with a high degree of substitution dissolves faster in cold water, and the resulting solution has a higher viscosity and better thickening effect. In addition, HEC solutions have good surface activity, thickening, stability and moisturizing properties, which make them widely used in different industries.

#### 1.3 Stability and Compatibility

HEC has good chemical and biological stability, and can remain stable in a wide pH range (usually between pH 3 and 11), and is not easy to degrade or deteriorate. In addition, HEC has good compatibility with a variety of ionic and non-ionic surfactants, thickeners and other additives, so it is often used in complex systems to improve its performance.

### 2. Preparation process of hydroxyethyl cellulose

HEC is usually prepared by reacting natural cellulose with ethylene oxide under alkaline conditions. The preparation process can be divided into the following main steps:

#### 2.1 Alkalization treatment

First, natural cellulose (such as wood pulp or cotton pulp) needs to be alkalized, that is, soaked in alkaline solution (such as sodium hydroxide) to activate the hydroxyl groups in cellulose, which is convenient for the subsequent etherification reaction. The alkalized cellulose will become a reaction intermediate.

#### 2.2 Etherification reaction

Ethylene oxide is added to the cellulose after alkalization treatment to carry out etherification reaction. This reaction is carried out at a certain temperature and pressure. Ethylene oxide reacts with the hydroxyl groups in cellulose to generate hydroxyethyl groups, which denatures cellulose into HEC. By controlling the reaction conditions and reaction time, the degree of substitution and molecular weight of HEC can be adjusted, thereby adjusting its final properties.

#### 2.3 Neutralization and purification

After the etherification reaction is completed, the reaction product needs to be neutralized to remove unreacted alkaline substances. Subsequently, the product is washed, filtered, dried and crushed to obtain the final HEC product. According to the application requirements, HEC can be further refined, such as screening, bleaching or surface treatment, to improve its application performance.

### 3. Main application areas of hydroxyethyl cellulose

#### 3.1 Construction and building materials

HEC is widely used in cement-based materials, gypsum products and coatings in the construction industry as a thickener, water retainer and binder.

- **Cement-based materials**: In cement-based materials such as mortar and concrete, HEC can effectively improve the viscosity and workability of the slurry and prevent the material from flowing or stratifying during construction. In addition, the water retention effect of HEC can prolong the hydration time of cement and improve the strength and durability of the finished product.

- **Gypsum products**: HEC is used as a water retainer and thickener in gypsum board, gypsum putty and gypsum powder to improve the construction performance and surface smoothness of gypsum.

- **Coatings**: In the coating industry, HEC, as a thickener and rheology control agent, can improve the fluidity and anti-sagging performance of the coating, ensuring uniform coating and good adhesion of the coating.

#### 3.2 Daily Chemicals and Cosmetics

HEC is commonly used as a thickener, stabilizer and emulsifier in daily chemicals and cosmetics.

- **Detergents**: In liquid detergents and shampoos, HEC can increase the viscosity of the product and improve the touch and feel of the product. At the same time, HEC also has a suspending effect to prevent the precipitation of particles in the detergent.

- **Skin Care**: HEC is used as a moisturizer and thickener in skin care products such as creams, lotions and cleansers. It can form a protective film on the skin surface, lock in moisture, prevent moisture loss, and improve the softness and smoothness of the skin.

- **Toothpaste**: HEC is used as a binder and thickener in toothpaste, which can make the toothpaste have a moderate viscosity, easy to extrude and evenly cover the tooth surface, while enhancing the film-forming and stability of the toothpaste.

#### 3.3 Petroleum Industry

During oil drilling and mining, HEC is widely used as a mud treatment agent and drilling fluid thickener.

- **Drilling fluid**: HEC as a thickener can increase the viscosity of drilling fluid, form a stable drilling mud, prevent wellbore collapse during drilling, and reduce mud filtration and improve drilling efficiency.

- **Fracturing fluid**: During hydraulic fracturing, HEC as a thickener can increase the viscosity of fracturing fluid, form an efficient fracture support fluid, enhance the fracturing effect, and increase the recovery rate of oil and natural gas.

#### 3.4 Papermaking Industry

HEC is mainly used for paper surface treatment and coating in the papermaking industry.

- **Surface sizing**: HEC is used as a thickener and adhesive in the process of paper surface sizing, which can improve the surface strength and water resistance of paper and improve the printing suitability of paper.

- **Coated paper**: In the production of high-grade coated paper, HEC, as a thickener and dispersant of the coating liquid, can improve the uniformity and coating quality of the coating liquid, ensure the smoothness of the paper surface, and enhance the gloss and printing effect of the paper.

#### 3.5 Pharmaceutical industry

In the pharmaceutical industry, HEC is used as an excipient for pharmaceutical preparations, especially in tablets and gels.

- **Tablets**: HEC is used as a binder in the preparation of tablets, which can improve the mechanical strength and stability of tablets. At the same time, it acts as a disintegrant to promote the rapid disintegration and drug release of tablets in the gastrointestinal tract.

- **Gel**: HEC is used as a thickener and film-forming agent in medical gels, which can form a stable gel system. It is used in wound dressings, ophthalmic preparations and skin protectants, and has good moisturizing and sustained release properties.

### 4. Future development and challenges of hydroxyethyl cellulose

Although HEC has performed well in many fields, it still faces some challenges in practical applications. For example, in building materials, due to the complex interaction between HEC's water retention and thickening effect and other additives, how to optimize the formula to achieve the best construction performance and cost-effectiveness remains a research focus. In addition, with the increasing awareness of environmental protection, the degradability and biocompatibility of HEC will also become an important direction for future development. Driven by new materials and new technologies, the application scope of HEC is expected to be further expanded. For example, its potential applications in the fields of renewable materials, biomedicine and smart materials are worthy of in-depth exploration and research.

### Summary

Hydroxyethyl cellulose (HEC), as an important

water-soluble polymer, plays an irreplaceable role in many industries with its unique physical and chemical properties and broad application prospects. By continuously improving the preparation process of HEC and optimizing the application formula, its performance can be further improved and its application range can be expanded. In future research and practice, the sustainability and efficiency of HEC will become the key direction of its development.