What viscosity of HPMC is suitable for putty powder?

Putty powder (or wall leveling material) is a material used for wall base treatment, and its main components include base material, filler and additives. The performance of putty powder has a crucial impact on the final effect of wall coating, and the additives used therein - especially hydroxypropyl methylcellulose (HPMC) - play a key role in improving the performance of putty powder.

### Overview of Hydroxypropyl Methylcellulose (HPMC)

HPMC is a non-ionic cellulose ether, which is obtained by reacting natural cellulose with propylene oxide and methyl chloride after alkali treatment. HPMC mainly plays the role of thickening, water retention, lubrication and improving construction performance in building materials.

### The role of HPMC in putty powder

1. **Thickening effect**:

- **Affecting construction performance**: HPMC, as a thickener, can effectively increase the consistency of putty powder, thereby improving construction performance. The appropriate consistency makes the putty powder not easy to sag during construction, and the coating is smooth.

- **Prevent drooping**: When constructing on vertical walls, proper consistency can prevent putty powder from sagging, improving operation efficiency and construction quality.

2. **Water retention**:

- **Extend open time**: HPMC has excellent water retention, which prevents the putty powder from drying quickly after construction, thereby extending the operation time and giving construction workers more time to adjust and repair.

- **Prevent cracking**: Good water retention can maintain moisture in putty powder, avoid cracking and peeling problems caused by rapid water loss, and improve the overall quality of the coating.

3. **Improve adhesion**:

- **Enhance substrate adhesion**: HPMC can improve the adhesion between putty powder and substrate, making putty powder more firmly attached to the wall and not easy to fall off.

- **Improve surface smoothness**: Proper viscosity can also make the surface of putty powder smoother, which is convenient for subsequent paint or coating construction.

### Suitable HPMC viscosity selection

The viscosity of HPMC has a direct impact on the final performance of putty powder. The following aspects need to be considered when choosing the right viscosity:

1. **Constructibility requirements**:

- **Manual construction**: Generally, manual construction requires a higher consistency of putty powder, so it is recommended to use HPMC with a viscosity between 100,000 and 150,000cps (centipoise, 2% aqueous solution, 20°C). This viscosity can provide good consistency and water retention, ensuring the stability and ease of operation of the putty powder during construction.

- **Mechanical construction**: If it is mechanical construction, due to the use of construction equipment, the consistency of the putty powder can be appropriately reduced to ensure the smooth operation of the equipment. Therefore, it is recommended to use HPMC with a viscosity between 60,000 and 100,000cps. This viscosity can not only ensure the smooth progress of equipment construction, but also provide sufficient water retention and adhesion.

2. **Environmental factors**:

- **Climate conditions**: In a hot and dry environment, putty powder loses water quickly, so it is necessary to select high-viscosity HPMC (100,000 to 150,000cps) to enhance its water retention and prevent cracking. In a humid environment, medium-viscosity (60,000 to 100,000cps) HPMC can be selected to maintain suitable construction properties.

3. **Putty powder formula**:

- **Different formulas**: The types and proportions of base materials and fillers in putty powder are different, and the viscosity requirements of HPMC are also different. Generally speaking, high-content fillers require high-viscosity HPMC to improve its consistency, while high-content base materials may require medium-viscosity HPMC to balance its fluidity and water retention.

### Conclusion

It is crucial to select HPMC with the right viscosity in the formula of putty powder. Taking into account the construction requirements, environmental factors and formula characteristics, in general, manual construction recommends the use of HPMC with a viscosity between 100,000 and 150,000cps, while mechanical construction recommends the use of HPMC with a viscosity between 60,000 and 100,000cps. In addition, the specific selection needs to be adjusted in combination with the actual construction environment and formula requirements to ensure that the putty powder has good construction performance, water retention and adhesion, thereby ensuring the final quality of the wall coating.