Hydroxypropyl methylcellulose (HPMC) is a water-soluble polymer compound, which is widely used in building materials, especially in cement mortar and gypsum-based slurry as an important additive. It can improve the performance of the slurry, improve the construction effect, and increase the durability and operability of the product.

1. Role in cement mortar
Cement mortar is a building material composed of cement, fine aggregate, water and additives, which is used in wall, floor and other construction construction. The main role of HPMC in cement mortar includes the following aspects:

Improve operability
During the use of cement mortar, viscosity and fluidity are the key factors that determine the construction effect. As a water-soluble polymer, HPMC can form a mesh structure in the mortar, improve the fluidity of the mortar, and increase its construction and operability. Cement mortar using HPMC is more viscous, can be more easily attached to the wall, and is not easy to slip, which is convenient for construction workers to operate.

Delay cement hydration reaction and increase open time
Cement hydration reaction is the key process of cement hardening. HPMC can form a colloidal structure in the mortar, delay the hydration rate of cement, and prevent cement from condensing too quickly during construction, thereby increasing the open time of the mortar. The extended open time helps construction workers to maintain sufficient operating time when constructing on a large scale.

Improve anti-segregation and water retention
HPMC can improve the water retention of cement mortar, prevent premature evaporation of water, and keep enough water in the mortar during the cement hydration process after construction. In addition, HPMC can also prevent the separation of water and aggregate in the mortar and reduce the segregation of mortar. This is of great significance for laying mortar on a large area, especially in high temperature and dry environment.

Enhance the adhesion of mortar
The molecular structure of HPMC can form physical adsorption between cement particles and sand particles, enhancing the adhesion of mortar. This can improve the bonding performance of cement mortar on various substrates, especially on dry substrates or irregular surfaces.

Improve surface smoothness
Due to the lubricity of HPMC, the surface of cement mortar with HPMC added is smoother, reducing the roughness generated during the construction process and improving the appearance of the final coating. This is particularly important in interior decoration, wall plastering and other construction.

2. Role in gypsum-based slurry
Gypsum-based slurry is mainly composed of gypsum powder, water and additives, and is widely used in wall decoration, plastering and decoration. The role of HPMC in gypsum-based slurry is similar to that of cement mortar, but it also has some unique functions.

Improve fluidity and operability
Similar to cement mortar, the fluidity and operability of gypsum-based slurry directly affect the construction effect. HPMC can effectively increase the fluidity of gypsum slurry, prevent the slurry from being uneven and sticky during mixing or construction, and ensure smoother construction.

Delay gypsum setting time
The setting time of gypsum slurry is relatively short. HPMC can delay the setting reaction of gypsum, so that the slurry can maintain a longer open time during construction. This helps construction workers to fully operate when working on a large area and avoid construction difficulties caused by too fast solidification.

Improve water retention and crack resistance
Gypsum slurry often faces the problem of premature evaporation of water during construction, which will cause cracking on the slurry surface. HPMC can improve the water retention of the slurry, reduce the evaporation of water, thereby reducing the generation of cracks and improving the crack resistance of gypsum-based slurry.

Enhance adhesion
HPMC can improve the adhesion between gypsum-based slurry and different substrates, especially on substrates with rough or irregular surfaces. By improving the adhesion of the slurry, HPMC enhances the overall stability of the gypsum-based slurry and avoids problems such as later shedding.

Improve surface smoothness and decorativeness
Gypsum-based slurry is often used for decorative construction, so its surface smoothness and final appearance are very important. The addition of HPMC can make the gypsum slurry more delicate and smooth, reduce the pitting phenomenon that may occur during construction, and improve the final effect.

The role of HPMC in cement mortar and gypsum-based slurry is multifaceted. It significantly improves the construction performance and final effect of cement mortar and gypsum-based slurry by increasing the fluidity of the slurry, delaying cement hydration or gypsum solidification, improving water retention and crack resistance, and enhancing adhesion. Especially in the process of large-scale construction and decoration, the application of HPMC has greatly improved work efficiency and product quality, and has become an indispensable and important additive in building materials.