How Do the Properties of Cellulose Ether Affect the Application of Dry Mix Mortar？

There are two types of cellulose ether: ionic, such as sodium carboxymethyl cellulose (CMC), and non-ionic, such as hydroxypropyl methyl cellulose (HPMC), hydroxyethyl methyl cellulose (HEMC) and methyl cellulose (MC). Today, cellulose ether are widely used in construction chemicals in the world.

 

Cellulose ether, as a key additives in dry-mix mortar products, significantly impacts both performance and cost. There are two types of cellulose ether: ionic, such as sodium carboxymethyl cellulose (CMC), and non-ionic, such as hydroxypropyl methyl cellulose (HPMC), hydroxyethyl methyl cellulose (HEMC) and methyl cellulose (MC). Today, cellulose ether are widely used in construction chemicals in the world.

 

The most critical property of cellulose ether in construction is water retention ability. Without it, thin layers of freshly applied mortar too quickly dry, preventing proper cement hydration. This leads to insufficient hardening and weak bonding strength. Adding cellulose ether not only enhances water retention but also improves the plasticity and flexibility of the mortar, boosting its bond strength. The following section explores how the properties of cellulose ether influence the performance of dry-mix mortars.

 

 

1. Fineness of Cellulose Ether

 

The fineness of cellulose ether impacts its solubility in water. A finer particle size allows cellulose ether to dissolve more quickly, enhancing its water retention properties. Therefore, fineness is an important characteristic to consider. Typically, the residue of cellulose ether on a 0.212mm sieve should not exceed 8.0%.

 

2. Drying Weight Loss Rate

 

The drying weight loss rate refers to the percentage of mass lost when cellulose ether is dried at a specific temperature. A high drying weight loss rate indicates a reduction in the effective components of the cellulose ether, which can negatively affect its performance in downstream applications and increase purchase costs. Generally, the drying weight loss rate for cellulose ether should not exceed 5.0%.

 

3. Ash Content in Cellulose Ether

 

High ash content in cellulose ether can reduce the proportion of active ingredients, diminishing its performance in downstream applications. Sulfate ash content is a crucial indicator of cellulose ether quality. Typically, the ash content for HPMC, HEMC and MC should not exceed 3.0%.

 

4. Viscosity of Cellulose Ether

 

The water retention and thickening properties of cellulose ether largely depend on its viscosity and the amount used in cement slurry. Higher viscosity often correlates with better performance in these areas.

 

5. pH Value of Cellulose Ether

 

The pH of cellulose ether affects its stability, particularly at higher temperatures or during long-term storage, where viscosity may gradually decrease, especially in high-viscosity products. Therefore, controlling the pH is essential. The pH range for cellulose ether is generally required to be between 5 and 9.

 

6. Transmittance of Cellulose Ether

 

The transmittance of cellulose ether influences its effectiveness in building materials. Several factors affect transmittance, including (1) raw material quality, (2) alkalization process, (3) formulation ratio, (4) solvent ratio, and (5) neutralization process. For optimal performance, the transmittance of cellulose ether should be at least 80%.

 

7. Gel Temperature of Cellulose Ether

 

Cellulose ether is primarily used as a thickener, plasticizer, and water retention agent in cement products, making both viscosity and gel temperature critical indicators of its quality. Gel temperature helps identify the type of cellulose ether and is linked to its degree of substitution. Additionally, salts and impurities can influence the gel temperature. As the solution temperature rises, the cellulose polymer gradually loses water, causing a drop in viscosity. Once the gel point is reached, the polymer fully dehydrates and forms a gel. Therefore, cement product temperatures are typically maintained below the initial gel temperature. In this range, the lower the temperature, the higher the viscosity, resulting in improved thickening and water retention effects.