Hydroxypropyl Methylcellulose (HPMC) is a water-soluble polymer material widely used in many industries such as construction, coatings, and medicine. In recent years, the application of HPMC in building plaster mortar has gradually become a research hotspot, mainly because it can significantly improve the performance of mortar, enhance the operability of construction, and improve the crack resistance, water retention and adhesion of mortar.

1. Basic properties of HPMC
HPMC is a non-ionic polymer compound formed by chemical modification of natural plant cellulose. Its main characteristics are good water solubility, excellent adhesion, film-forming property, water retention, thickening and stability. By controlling the degree of substitution of hydroxypropyl and methyl groups, its different physical and chemical properties can be adjusted, which allows HPMC to play a role in different industrial applications.

2. The role of HPMC in plaster mortar
2.1 Improve water retention
During the construction process of plaster mortar, especially under dry conditions, the surface often dries prematurely due to rapid evaporation of water, thus affecting the bonding strength and crack resistance of the mortar. HPMC, as a water-soluble polymer, can improve the water retention of the mortar and delay the evaporation of water. The hydroxyl and methyl groups in its molecules can form hydrogen bonds with water molecules, thereby reducing water loss. This effect not only helps to improve the construction performance of the mortar, but also effectively avoids cracking caused by rapid evaporation of water.

2.2 Improve construction performance
The construction performance of plaster mortar, especially the operability of construction, is an important factor affecting the construction quality. HPMC can effectively improve the fluidity and plasticity of the mortar, making it easier for construction workers to evenly apply the mortar during the construction process to avoid weak bonding or stratification. In addition, HPMC can also reduce the adhesion and separation of the mortar, ensuring that the mortar is not easy to flow or slide during the construction process, especially on the vertical surface.

2.3 Improve crack resistance
During the hardening process, mortar is often prone to cracking due to the heat generated by cement hydration, the water absorption of the substrate and changes in the external environment. The introduction of HPMC can effectively reduce the occurrence of this problem. It can improve the cohesion of the mortar, making it less likely to crack during the drying process. In addition, HPMC also has a certain improvement effect on the microstructure of cement-based materials, which can reduce the shrinkage of the mortar during the drying process to a certain extent, and further enhance the crack resistance.

2.4 Enhance adhesion
As a surfactant, HPMC can improve the adhesion between the mortar and the substrate. Whether it is in contact with different substrates such as concrete, brick walls or gypsum boards, HPMC can enhance the adhesion of the mortar and prevent the mortar from falling off or cracking. On the contact surface of various substrates, HPMC can form a uniform protective film to improve the bonding strength, thereby enhancing the durability of the mortar.

2.5 Improve impermeability
In a humid environment, the impermeability of plaster mortar is particularly important. HPMC can enhance its impermeability by improving the compactness of the mortar. The hydroxyl and methyl groups in the HPMC molecule can form a denser structure in the mortar, which not only helps prevent moisture penetration, but also increases the service life of the mortar in harsh environments.

3. Specific application of HPMC in plaster mortar
3.1 Internal and external wall plaster mortar
Internal and external wall plaster mortar is one of the most widely used areas for HPMC. Since the exterior walls of buildings need to face strong weather changes and temperature differences, the exterior wall mortar especially needs to have good crack resistance and water resistance. The water retention and crack resistance of HPMC make it extremely important in exterior wall mortar. The interior wall mortar mainly improves construction efficiency and quality by improving construction performance, fluidity and adhesion.

3.2 Decorative mortar
With the diversification of architectural decoration styles, the demand for decorative mortar is increasing. In this type of mortar, HPMC can improve the plasticity of the mortar, allowing construction workers to perform various decorative treatments on large areas of walls. The excellent fluidity and water retention of HPMC enable the mortar to maintain good stability during the drying process, avoiding uneven cracking or surface shedding.

3.3 Repair mortar
In building repair projects, the adhesion and impermeability of mortar are crucial. HPMC can enhance the adhesion of mortar, so that the repair mortar can better combine with the original wall surface, avoiding the fall-off of the repair layer or the appearance of hollowing. In addition, HPMC can effectively extend the service life of the repair mortar and reduce the cracking of the repair layer.

The application of hydroxypropyl methylcellulose (HPMC) in plaster mortar can not only significantly improve the water retention, crack resistance, construction performance, adhesion and impermeability of the mortar, but also improve the overall performance of the mortar to meet the needs of different building environments. With the continuous advancement of HPMC technology and the expansion of its application fields, its application prospects in the construction industry are very broad, and it can provide strong support for the construction quality and durability of construction projects.