1. Introduction to HPMC
Hydroxypropyl methylcellulose (HPMC) is an important water-soluble polymer compound widely used in construction, medicine, food, daily chemicals and other fields. It is made from chemically modified natural cellulose and has good water solubility, thickening, water retention, adhesion, film-forming and lubrication properties. In building materials, HPMC is particularly widely used as an additive, especially in gypsum-based building materials.

2. The role of HPMC in gypsum-based building materials
Gypsum-based building materials, such as gypsum putty, gypsum mortar and gypsum board, are gradually being widely used due to their fire resistance, breathability and environmentally friendly properties. The introduction of HPMC can improve the physical and construction properties of these materials, making them more convenient and durable during use, and provide better appearance.

2.1 Thickening effect
The thickening effect of HPMC is one of its main functions in gypsum-based building materials. It significantly increases the viscosity of gypsum slurry, making it easier to handle and apply. The function of the thickener can keep the gypsum-based materials in a uniform slurry state during the construction process, reduce precipitation, avoid uneven layers, and ensure the quality and effect of the construction.

2.2 Water retention
HPMC has excellent water retention properties and can reduce the loss of water in gypsum-based materials during the curing process. Water retention is an important factor in ensuring the performance of gypsum materials. Excessive water loss will cause the material to dry prematurely, which will affect the strength and bonding performance, and may even lead to cracks. By adding HPMC, the gypsum material can retain sufficient moisture for a longer period of time, thereby helping the material to cure evenly and improving strength and surface quality.

2.3 Improve construction performance
HPMC can also improve the construction performance of gypsum-based materials, especially in improving workability. It gives the slurry good thixotropy and ensures easy application of the slurry during construction. Its lubrication effect can also make construction smoother, reduce friction between tools and materials, and further improve efficiency and effectiveness. For both manual construction and mechanical spraying, HPMC can significantly improve operating comfort.

2.4 Resistance to sagging
In vertical construction such as walls or ceilings, gypsum materials are prone to sagging due to gravity, especially when constructing thick coatings. The thickening and bonding-enhancing properties of HPMC can effectively improve the sagging resistance of gypsum slurry, making it have stronger adhesion on vertical surfaces and maintain uniformity of shape and thickness after construction.

2.5 Improve crack resistance
Gypsum-based materials may develop cracks due to evaporation of water during the drying process. The water retention performance of HPMC not only extends the opening time of the gypsum material, but also reduces the volume shrinkage caused by excessive water loss by reducing the rapid evaporation of internal water, thereby effectively reducing the occurrence of cracks and enhancing the stability and stability of the gypsum material. service life.

3. How to use HPMC
In gypsum-based building materials, the addition amount of HPMC is usually between 0.1% and 1% of the overall formula. The specific usage varies according to different application scenarios and performance requirements. For example, when used in gypsum putty, HPMC is mainly used to improve its water retention and construction performance, so the amount added is relatively small; while in gypsum mortar, especially in mortar formulas that require enhanced crack resistance, the amount of HPMC used Probably slightly higher. In addition, the solubility of HPMC also has a great influence on the use effect. It usually needs to be evenly dispersed when preparing gypsum slurry to ensure that it can fully exert its effect.

4. Factors affecting the performance of HPMC
The performance of HPMC is affected by many factors, including its molecular weight, degree of substitution (i.e., the degree of substitution of methoxy and hydroxypropoxy groups), particle size, etc. Generally speaking, the higher the molecular weight, the stronger the thickening effect of HPMC; the higher the degree of substitution, the better its solubility and water retention. Therefore, among gypsum-based building materials, it is crucial to select the appropriate HPMC model.

Environmental conditions such as temperature, humidity and other ingredients in the gypsum material can also affect the performance of HPMC. For example, in high-temperature environments, the dissolution rate and water retention of HPMC will decrease. Therefore, in actual construction, the formula needs to be adjusted appropriately based on site conditions.

5. Application advantages of HPMC in gypsum-based materials
The application of HPMC in gypsum-based building materials has multiple advantages and can significantly improve the construction performance of the material and the quality of the finished product:

Improve material strength: HPMC improves the water retention of gypsum materials and makes the hydration reaction more complete, thereby improving the strength of the material.
Optimize the construction process: The thickening and lubricating effects of HPMC can significantly improve the smoothness of construction and reduce sagging and sagging.
Extended operable time: HPMC extends the open time of the material by keeping the slurry properly moist, giving construction workers more room for adjustment.
Improve surface finish: HPMC can reduce cracks and bubbles in gypsum materials, ensuring a smooth and flat surface after drying.

The application of hydroxypropyl methylcellulose (HPMC) in gypsum-based building materials not only improves the physical properties of the material, but also significantly improves construction quality and efficiency. Its functions of thickening, water retention, and crack resistance make gypsum-based materials more widely used in modern buildings. By selecting appropriate HPMC models and formulas, construction engineers and construction personnel can obtain ideal use effects in different application scenarios, providing a strong guarantee for the quality and durability of buildings.