Hydroxypropyl methyl cellulose, as the main additive in building dry mix mortar products, plays a crucial role in the performance and cost of dry mix mortar. Currently, most cellulose ether products worldwide are used for building materials. The important performance of cellulose ether is its water retention in building materials. If cellulose ether is not added, the thin layer of freshly mixed mortar will dry quickly, making it impossible for the cement to hydrate in a normal way, resulting in the mortar being unable to harden and achieve good adhesion. At the same time, the addition of cellulose ether makes the mortar have good plasticity and flexibility, improving the bonding strength of the mortar

1. Fineness of Hydroxypropyl Methyl Cellulose

The fineness of cellulose ether affects its solubility. The finer the cellulose ether, the faster its dissolution rate in water and the improved its water retention performance. Therefore, the fineness of cellulose ether should be included as one of its properties under investigation. Generally speaking, cellulose ether with a fineness of 80 mesh passes through completely.

2. Drying weight loss rate of hydroxypropyl methyl cellulose

Drying loss rate refers to the percentage of material mass lost during the drying of cellulose ether at a certain temperature compared to the original sample mass. For a certain quality of cellulose ether, if the drying weight loss rate is too high, it will reduce the content of active ingredients in cellulose ether, affect the effectiveness of downstream enterprise applications, and also increase the purchase cost. Normally, the drying weight loss rate of cellulose ether is not greater than 5.0%.

Sulfate ash of hydroxypropyl methyl cellulose

For a certain quality of cellulose ether with high ash content, it will reduce the content of active ingredients in cellulose ether, affecting the effectiveness of downstream enterprise applications. The sulfate ash content of cellulose ether is an important indicator of its own performance. Based on the current production status of cellulose ether production enterprises in China, the ash content of MC, HPMC, and HEMC is usually not more than 5%.

3. Viscosity of Hydroxypropyl Methyl Cellulose

The water retention and thickening effects of hydroxypropyl methyl cellulose mainly depend on the viscosity and dosage of the cellulose ether added to the cement slurry.

PH value of hydroxypropyl methyl cellulose

Hydroxypropyl methylcellulose products experience a gradual decrease in viscosity at higher temperatures or after prolonged storage, with high viscosity products showing particularly significant performance. Therefore, it is necessary to limit the acidity and alkalinity. It is generally required that the pH range of cellulose ether be controlled between 5-9.

4. Transmittance of Hydroxypropyl Methyl Cellulose

The light transmittance of hydroxypropyl methyl cellulose directly affects its application effect in building materials. The main factors affecting the light transmittance of cellulose ether are:

(1) The quality of raw materials;

(2) The effect of alkalization;

(3) Process ratio;

(4) Solvent ratio;

(5) The neutralization effect.

According to the usage effect, the transmittance of cellulose ether should not be less than 80%.

5. gel temperature of HPMC

Hydroxypropyl methyl cellulose is mainly used as a tackifier, plasticizer and water retaining agent in cement products, so viscosity and gel temperature are important indicators of hydroxypropyl methyl cellulose. The gel temperature is used to determine the type of cellulose ether, which is related to the degree of substitution of cellulose ether.

In addition, salt and impurities will also affect the gel temperature. When the solution temperature rises, the cellulose polymer gradually loses water, and the solution viscosity decreases. When it reaches the gel point, the polymer is completely dehydrated to form gel. Therefore, the temperature in cement products is usually controlled below the initial gel temperature. Under this condition, the lower the temperature, the higher the viscosity, and the more obvious the viscosity and water retention effect.