Effects of etherification degree and temperature on water retention of cellulose ethers.

Cellulose ethers are a class of polymer materials obtained by chemical modification of natural cellulose and are widely used in the fields of construction, pharmaceuticals, food, etc. The water retention of cellulose ethers is a key performance in a variety of applications, which is mainly affected by its etherification degree and use temperature. This article will discuss in detail the effects of etherification degree and temperature on water retention of cellulose ethers, covering its chemical structure, mechanism of action, experimental data and practical applications.

## 1. Chemical structure and water retention of cellulose ethers

### 1.1 Basic structure of cellulose ethers

Cellulose ethers are formed by the replacement of hydroxyl groups (—OH) of cellulose by substituents. Common cellulose ethers include hydroxypropyl methylcellulose (HPMC), methyl cellulose (MC), carboxymethyl cellulose (CMC), etc. The chemical structure of these cellulose ethers determines their solubility and water retention.

### 1.2 Definition and importance of water retention

Water retention refers to the ability of a material to retain moisture after absorbing water. In building materials, water retention has an important influence on the performance of the material. For example, in cement mortar, good water retention can prolong the hydration reaction time of cement, improve the strength and adhesion of mortar, and prevent shrinkage and cracking.

## 2. Effect of etherification degree on water retention of cellulose ether

### 2.1 Definition of etherification degree

The degree of substitution (DS) refers to the number of hydroxyl groups substituted in each glucose unit. The higher the DS value, the higher the degree of substitution of cellulose ether. Different types of cellulose ethers have different DS values and different performances.

### 2.2 Effect of etherification degree on water retention

- **Low etherification degree**: When the DS value of cellulose ether is low, the solubility and water retention are poor. Because cellulose ether with low etherification degree has low solubility in water, it is difficult to form a uniform solution, resulting in poor water retention.

- **Medium etherification degree**: When the DS value of cellulose ether is at a medium level, the solubility and water retention are good. Cellulose ether with medium etherification degree can form a relatively stable solution in water, provide good water retention effect, and is suitable for a variety of building materials.

- **High degree of etherification**: When the DS value of cellulose ether is higher, the solubility and water retention are further improved. However, too high a degree of etherification may cause the solubility of cellulose ether in some solvents to be too high, affecting its use effect in some applications.

### 2.3 Experimental data support

Experimental studies have shown that the water retention properties of cellulose ethers with different degrees of etherification in cement mortar are significantly different. Taking HPMC as an example, HPMC with a DS value of 1.2-1.5 has the best water retention and can significantly improve the crack resistance and strength of mortar.

## 3. Effect of temperature on water retention of cellulose ether

### 3.1 Effect of temperature on solubility

The solubility of cellulose ether varies at different temperatures. Generally speaking, cellulose ether has better solubility at low temperatures, and its solubility gradually decreases as the temperature increases. This is because under high temperature conditions, the hydrogen bonding effect between cellulose ether molecules is enhanced, resulting in a decrease in solubility.

### 3.2 Effect of temperature on water retention

- **Low temperature environment**: In a low temperature environment, cellulose ether has better water retention. This is because cellulose ether has high solubility at low temperatures, can fully absorb and retain moisture, and improve the construction performance and durability of building materials.

- **Medium temperature**: At medium temperature, the water retention of cellulose ether is still good, but slightly lower than that in low temperature environment. Under medium temperature conditions, the solubility of cellulose ether decreases slightly, but it can still maintain a high water retention effect.

- **High temperature environment**: Under high temperature environment, the water retention of cellulose ether is significantly reduced. Under high temperature conditions, the hydrogen bonding effect between cellulose ether molecules is enhanced and the solubility decreases, making it difficult to fully absorb and retain moisture, affecting the performance of building materials.

### 3.3 Experimental data support

The experimental data show that the water retention performance of cellulose ether changes significantly at different temperatures. At 20℃, the water retention rate of cellulose ether is the highest, which can reach more than 90%; at 40℃ and 60℃, the water retention rate gradually decreases to about 80% and 70% respectively.

## 4. Considerations in practical applications

### 4.1 Selecting the appropriate degree of etherification

In practical applications, cellulose ethers with appropriate degrees of etherification need to be selected according to specific requirements. For example, in building mortar, HPMC with a DS value of 1.2-1.5 can provide the best water retention and construction performance; in other special applications, the degree of etherification may need to be adjusted to meet specific needs.

### 4.2 Controlling the construction environment temperature

During the construction process, the ambient temperature needs to be controlled to ensure the water retention of cellulose ether. When constructing in a high temperature environment, measures such as shading and water spraying can be taken to reduce the ambient temperature, maintain the water retention of cellulose ether, and improve the construction quality.

### 4.3 Use with other additives

In some cases, other additives such as thickeners and water retaining agents can be used in combination to further improve the water retention of cellulose ether. For example, in a high temperature environment, a small amount of thickener can be added to enhance the water retention of cellulose ether and ensure the construction quality.

## 5. Conclusion

In summary, the etherification degree and temperature of cellulose ether have a significant effect on its water retention. Moderate etherification degree and suitable temperature can provide the best water retention effect and significantly improve the construction performance and durability of building materials. In practical applications, by reasonably selecting the etherification degree of cellulose ether, controlling the construction environment temperature and using it with other additives, the water retention performance of cellulose ether can be maximized to meet the needs of various construction and industrial fields. In the future, with the continuous development of cellulose ether technology, it will continue to make new progress in optimizing water retention performance and promote technological progress and innovation in building materials and other application fields.