2024-08-06- readingsI. Introduction
The application of cellulose ether, especially hydroxypropyl methylcellulose (HPMC), in dry-mixed mortar is of great significance. As a high-performance additive, HPMC greatly improves the quality and performance of dry-mixed mortar through its thickening, water retention, and improved construction performance. This article will introduce in detail the chemical properties of HPMC, its mechanism of action in dry-mixed mortar, its specific applications and the performance advantages it brings, in order to provide a comprehensive reference for professionals in related fields.
### II. Chemical properties of HPMC
HPMC is a non-ionic cellulose ether obtained by methylation and hydroxypropylation of natural cellulose. Its chemical structure consists of a cellulose backbone and evenly distributed methyl and hydroxypropyl substituents. The specific characteristics are as follows:
1. **Solubility**: HPMC has good water solubility and can be evenly dissolved in cold and hot water to form a transparent or milky colloidal solution.
2. **Viscosity**: HPMC solution has good viscosity and rheology, and the viscosity range can be adjusted according to different molecular weights and substitution degrees.
3. **Water retention**: HPMC has excellent water retention capacity, can keep materials moist in dry environments, and promote the full hydration of cement and other cementitious materials.
4. **Stability**: HPMC has excellent chemical stability, thermal stability and pH stability, and can remain stable in a wide pH range.
5. **Biocompatibility**: HPMC has good biocompatibility and low allergenicity, and is suitable for use in various building materials.
### 3. Mechanism of action of HPMC in dry-mixed mortar
#### 1. Thickening effect
One of the main functions of HPMC in dry-mixed mortar is thickening. It increases the viscosity of the mortar, making the mortar suitable for workability and anti-sagging. The thickening effect ensures that the mortar is not easy to slip during vertical construction, improving the construction quality.
#### 2. Water retention
The water retention of HPMC is the key feature of its application in dry-mixed mortar. HPMC forms a water-retaining film inside the mortar, reduces the evaporation and penetration of water, prolongs the hydration time of cement, and ensures that the mortar obtains sufficient water during the hardening process, thereby improving its strength and durability.
#### 3. Improve construction performance
HPMC can significantly improve the construction performance of dry-mixed mortar, including workability, thixotropy and anti-sagging. Its addition makes the mortar have good operability during the construction process, reduces the difficulty of construction, and improves construction efficiency.
#### 4. Enhanced bonding
By improving the cohesion and adhesion of the mortar, HPMC can significantly improve the bonding strength between the mortar and the substrate, ensure the construction quality, and reduce the risk of material shedding and cracking.
### 4. Specific application of HPMC in dry-mixed mortar
#### 1. Tile adhesive
The application of HPMC in tile adhesive is particularly important. Its high viscosity and excellent water retention can improve the viscosity and water retention of tile adhesives, enhance their bonding strength and durability. At the same time, HPMC can also improve the construction performance of adhesives, reduce slippage in vertical construction, and improve construction efficiency and quality.
#### 2. External wall insulation system
In the external wall insulation system, HPMC can improve the viscosity and water retention of insulation mortar, enhance its bonding force and crack resistance, and ensure the overall stability and weather resistance of the insulation system. At the same time, HPMC can also improve the construction performance of insulation mortar and reduce the occurrence of hollows and cracks.
#### 3. Self-leveling mortar
HPMC plays a thickening and water retention role in self-leveling mortar. It improves the viscosity and fluidity of the mortar, so that the self-leveling mortar has good self-leveling performance and construction performance. At the same time, the water retention of HPMC can prevent the mortar from losing water too quickly during the hardening process, ensuring the strength and surface finish of the self-leveling mortar.
#### 4. Repair mortar
In repair mortar, HPMC can improve the viscosity and water retention of mortar, ensuring that the repair mortar has good bonding strength and durability after construction. HPMC can also enhance the flexibility and crack resistance of repair mortar, and extend the service life of the repair effect.
#### 5. Waterproof mortar
HPMC can improve its water retention and viscosity in waterproof mortar, and enhance the density and impermeability of waterproof mortar. At the same time, HPMC can also improve the flexibility of waterproof mortar, prevent cracks when the substrate is deformed, and ensure the waterproof effect.
### 5. Performance advantages of HPMC in dry-mixed mortar
1. **Excellent water retention**: HPMC has excellent water retention, which can effectively extend the hydration time of cement and gypsum, promote their full hydration, and improve the strength and durability of mortar.
2. **Good thickening and thixotropy**: The thickening and thixotropy of HPMC make the dry-mixed mortar have good operating performance during the construction process, ensuring the stability of the mortar in vertical and horizontal construction.
3. **Improving bond strength**: By improving the cohesion and adhesion of the mortar, HPMC significantly improves the bond strength of the dry-mixed mortar, ensuring the construction quality and service life.
4. **Improving construction performance**: HPMC can improve the workability, fluidity and anti-sagging of the dry-mixed mortar, reduce the difficulty of construction, and improve construction efficiency and quality.
5. **Enhancing durability**: HPMC improves the flexibility and crack resistance of the mortar, enhances its adaptability to environmental changes, and extends the service life of the mortar.
6. **Reduce cracking**: The water retention and thickening effect of HPMC can effectively prevent the dry-mixed mortar from losing water quickly during the drying process, thereby reducing cracking and peeling.
### VI. Conclusion
As a high-performance construction chemical, cellulose ether HPMC has significant performance advantages in the application of dry-mixed mortar. It significantly improves the construction performance and service life of dry-mixed mortar through various mechanisms such as thickening, water retention, improving bonding strength and improving construction performance. With the continuous development of construction technology and the continuous improvement of the performance requirements of building materials, HPMC will play a more important role in the field of construction chemicals and provide strong support for the development of the construction industry.
