Application of HPMC in cement-based plasters and plasters

1. Overview of HPMC
HPMC (Hydroxypropyl Methylcellulose, hydroxypropyl methylcellulose) is a water-soluble polymer compound obtained by chemical modification of natural cellulose. It has good water solubility, film-forming properties, thickening properties, adhesion, water retention and rheology, and is widely used in construction, coatings, medicine, food and other industries. In the construction industry, especially in cement-based plaster and stucco, HPMC, as an additive, can significantly improve the construction performance, physical properties and durability of the material, becoming an important additive to improve the quality of building materials.

2. Application of HPMC in cement-based plastering and stucco
Improve construction performance
During the construction process of cement-based plaster and stucco, HPMC can significantly improve the fluidity and ductility of the slurry, making the construction process smoother and more uniform. The specific performance is:

Extend the opening time: HPMC can delay the initial setting time of cement, thereby increasing the opening time of the material. This allows construction workers to operate for a longer period of time, especially when constructing large areas, and prevents the cement slurry from solidifying too quickly and affecting the construction effect.
Improve adhesion: Cement-based plaster and stucco are often used for bonding between different base surfaces. HPMC can effectively improve adhesion, reduce coating peeling, and ensure the stable adhesion of the plaster layer or stucco layer.

Improve water retention
In cement-based plasters and plasters, the water-retaining role of HPMC is particularly important. The water in cement slurry evaporates quickly, especially in high temperature and dry environments, which can easily lead to incomplete cement condensation, thus affecting the strength and durability of the plaster layer or mortar. By improving the water retention of the material, HPMC can slow down the evaporation rate of water and fully hydrate the cement, thereby increasing the strength of the cement-based plaster layer or mortar layer and ensuring the construction effect.

Enhance crack resistance
Since cement-based plaster and stucco materials generate internal stress during the hardening process, they are prone to cracks, especially in dry environments with large temperature differences. HPMC can effectively reduce the occurrence of dry cracking by improving the rheology and water retention of cement slurry. In addition, the adhesion of HPMC improves the bonding force between the plaster layer and the base layer, reduces the formation of cracks caused by external forces, and improves the crack resistance of the plaster layer.

Improve rheology
HPMC is used as a thickener in cement-based plasters and plasters, which can significantly improve the rheological properties of the slurry. It can make the slurry have better fluidity and appropriate viscosity, avoiding construction problems that are too dense or too thin. For example, HPMC can improve the suspension of slurry, so that fine particles in cement slurry can be evenly distributed, avoid settlement, and ensure smoother and more uniform plaster construction.

Washing resistance
HPMC can improve the water-wash resistance of cement-based plaster and stucco and reduce water erosion on the slurry surface in humid environments. If the cement slurry surface lacks sufficient water resistance, it will affect the hardening speed and strength of the cement. HPMC can enhance the water resistance of cement-based plasters and plasters to avoid excessive erosion by external moisture, thus improving the durability of the coating.

3. Dosage and application recommendations of HPMC
The dosage of HPMC usually depends on the type of cement-based render or stucco and its performance requirements. Generally speaking, the amount of HPMC added is about 0.1%-0.5% of the cement mass, but the specific amount needs to be adjusted according to the actual situation. For example, in some special applications, higher addition levels may be required to enhance the material’s adhesion, water retention, or rheology.

When using HPMC, you need to pay attention to the following points:
Uniform mixing: HPMC has poor dispersion in cement-based plasters and plasters. When using it, ensure that it is fully mixed with other ingredients to avoid agglomeration.
Storage conditions: HPMC has a certain degree of hygroscopicity and should be stored in a dry environment to avoid moisture absorption leading to a decrease in its performance.
Cooperation with other additives: When used in a composite additive system, it is necessary to ensure the compatibility of HPMC with other chemical additives to avoid affecting the overall performance.

4. Advantages and challenges of HPMC

Advantages:
Environmental protection: As a natural polymer material, HPMC has sustainable sources of raw materials and has less burden on the environment.
Enhance construction performance: HPMC can effectively improve the construction performance of cement-based plaster and stucco, making the construction process more convenient and faster.
Improved durability: Enhances the water retention, crack resistance and water wash resistance of cement-based plasters and plasters, extending the service life of building materials.

challenge:
Cost issue: The cost of HPMC is relatively high, especially when used on a large scale, which may increase the overall cost of materials.
Proportion problem: HPMC has different effects in different types of cement-based materials, and improper proportioning may affect the final performance.

As a high-performance construction additive, HPMC has wide application value in cement-based plaster and stucco. By improving construction performance, increasing water retention, enhancing adhesion, and improving crack resistance, HPMC can significantly improve the performance of cement-based materials and meet the high requirements of the modern construction industry for material quality and construction efficiency. However, the application of HPMC also needs to be combined with actual engineering needs and its dosage and ratio should be reasonably selected to ensure its best effect in building materials.