Hydroxypropyl methylcellulose (HPMC, Hydroxypropyl Methylcellulose) is a commonly used water-soluble polymer compound that is widely used in the construction industry, especially in putty powder, coatings and other materials. HPMC not only has good rheological properties, water retention, and thickening properties, but can also improve the operability and adhesion of putty powder. For the formula design of putty powder, a reasonable amount of HPMC has an important impact on the quality, construction performance and economy of the product.

1. The role and function of HPMC
As a key additive in putty powder, HPMC has the following main functions:

Thickening effect: HPMC can increase the viscosity of putty powder and improve its rheology. By adjusting the amount of HPMC added, the consistency of the putty powder and the thickness during construction can be controlled to ensure that the putty can be evenly coated on the wall.

Water retention: HPMC can significantly improve the water retention performance of putty powder, extend the opening time of putty powder, and avoid premature drying and cracking of materials during the construction process. This is especially important when applying over large areas, especially in hotter, dryer climates.

Improve adhesion: The use of HPMC in putty powder can increase the adhesion between it and the base material (such as cement wall, gypsum board, etc.), thus improving the bonding strength of the putty powder.

Improve surface finish: Due to the thickening effect of HPMC, putty powder can better fill small cracks in the wall, making the surface smooth and delicate, and improving the aesthetics.

2. The effect of HPMC dosage on the performance of putty powder
Construction performance
The amount of HPMC in putty powder directly affects its construction performance. An appropriate amount of HPMC can improve the fluidity and operability of putty powder. The common dosage range is 0.3%~1.0% (calculated based on the total weight of putty powder). When the HPMC dosage is low, the putty powder has a lighter consistency and may be sticky and slippery during construction, making it difficult to control the thickness; while an excessive HPMC dosage may cause the putty powder to be too dense and difficult to apply during construction, increasing labor intensity.

surface quality
The thickening effect of HPMC makes the putty powder have better construction stability. Especially during the construction process, the putty powder can evenly adhere to the wall surface and reduce the phenomenon of powder falling off. A moderate amount of HPMC can effectively control the drying speed of putty powder and avoid surface defects caused by dry cracking. Too low an HPMC dosage may cause the putty powder to dry too quickly and form cracks; while an excessively high dosage may cause the surface to be too smooth, easily leading to a decrease in adhesion and hollowing.

Hardness and Strength
The amount of HPMC also has a certain impact on the hardness and strength of putty powder. Generally speaking, when the amount of HPMC is low, the hardness and strength of the putty powder are poor, and loosening or crusting on the surface may occur within a few hours after construction; appropriately increasing the amount of HPMC can improve the crack resistance and strength of the putty powder. Strength, giving it better durability after hardening.

Water retention and drying speed
A distinctive feature of HPMC is that it can significantly improve the water retention of putty powder, which is crucial for operation during the construction process. When the dosage is low, the putty powder will easily lose water too quickly, and drying too quickly will lead to problems such as powder removal and cracking during construction. The appropriate amount of HPMC can keep the putty powder on the wall with sufficient moisture, ensuring that it has sufficient time for smoothing and trimming. When the dosage is too high, the putty powder may become excessively viscous, resulting in uneven drying of the surface after construction and affecting the smoothness of the putty layer.

Economy
Although HPMC has many excellent properties, as a functional additive, its cost is relatively high. Although excessive use of HPMC can improve the performance of putty powder, it will also significantly increase production costs. Therefore, in the production process of putty powder, the usage of HPMC needs to be reasonably controlled according to specific needs and economic requirements to achieve a balance between performance and cost.

3. Differences in volume of different types of HPMC
HPMC is divided into different types according to different modification methods, such as HPMC with low degree of substitution and high degree of substitution. The effect of its use in putty powder may be different. HPMC with a low degree of substitution usually has strong thickening and long opening time, and is suitable for putty powder that requires a long operating time; while HPMC with a high degree of substitution can improve the fluidity and fluidity of the putty powder in a short time. Constructability. According to the different types of HPMC, the dosage range will also be adjusted. Generally, the dosage of low-substitution HPMC is slightly higher.

The amount of HPMC used in putty powder has a direct impact on the performance of putty powder. Appropriate dosage can improve the construction performance of putty powder, improve surface quality, enhance water retention, improve adhesion and increase strength. However, using too much or too little can negatively affect the performance of the putty powder. To sum up, the reasonable HPMC dosage should be comprehensively considered based on the specific application requirements of putty powder, construction environment, economic cost and other factors. By optimizing the amount of HPMC, the performance and quality of putty powder can be effectively improved to meet the needs of the market and users.