Application of HPMC in putty powder and analysis of the cause of foaming of putty powder

1. The role of HPMC in putty powder
Hydroxypropyl methylcellulose (HPMC) is a common additive in putty powder, and its main functions are reflected in the following aspects:

Enhance construction performance
HPMC has good water retention and lubricity, which can improve the workability of putty powder, prolong the open time, and facilitate construction operations. Water retention can keep the putty powder in a proper moist state during construction, preventing construction difficulties caused by premature drying.

Improve crack resistance
After adding HPMC to putty powder, the flexibility and adhesion of putty are enhanced, which can effectively reduce the cracking of the wall caused by shrinkage or temperature difference.

Improve surface effect
HPMC has certain film-forming and adhesive properties, which can improve the spreadability of putty powder, making the surface of the putty after application smooth and smooth, without obvious brush marks or flow marks.

Improve bonding strength
HPMC can enhance the adhesion between putty and the base layer, and prevent the putty layer from peeling or powdering.

Adjust construction properties
The addition of HPMC can adjust the consistency and thixotropic properties of putty powder, so that putty powder can better adapt to the requirements of manual or mechanical spraying construction.

2. Causes of putty powder bubbling
In the actual construction process, putty powder bubbling is a common problem. The main reasons can be summarized as follows:

Improper base treatment
The wall base is too rough, and there are cracks, holes or loose materials on the surface, which causes gas to seep out from these uneven places to form bubbles after the putty powder is applied.

Too high or too low moisture content of the wall can also easily lead to bubbling problems.

Material ratio problem
Excessive HPMC and cellulose content in putty powder will enhance water retention, but excessive water retention may cause bubbles in the putty during curing.
If the ratio of additives such as glue powder is uneven, it may cause putty instability, which is easy to bubble.

Insufficient stirring
Putty powder is not stirred evenly when mixed with water, resulting in more gas in the slurry. These gases are not completely discharged during application, forming bubbles.

Improper construction method
When scraping putty, the operation technique is not stable, or the scraping speed is too fast, which may cause air to be drawn into the putty layer.
If the putty layer is too thick, it is easy to produce bubbles if too much is applied at one time, especially in the case of thick coating, the gas is more difficult to discharge.

Influence of environmental factors
When the humidity of the construction environment is high, the evaporation of water is hindered, and the gas in the putty is more likely to be retained, resulting in the formation of bubbles.
When the construction temperature is too high, the water evaporates too quickly, which may also cause the bubbles in the putty layer to fail to be discharged in time.

Quality problems of putty powder
If the quality of raw materials in the production process of putty powder is not up to standard, or the production process is not perfect, it will also cause the putty to bubble easily during construction.

3. Suggestions for solving the problem of putty powder bubbling
Base treatment
Ensure that the wall surface is clean and flat, without obvious cracks, holes or loose materials. Use interface agent for base treatment when necessary.
Control the moisture content of the wall within an appropriate range (generally not more than 10%).

Optimize putty formula
Adjust the amount of HPMC added according to specific construction conditions to avoid excessive water retention and bubbling.
Use putty powder raw materials with stable quality and strictly follow the proportion to ensure uniform composition.

Standardized construction operation
Ensure uniformity during stirring to avoid introducing too much air. After stirring, let it stand for 5 to 10 minutes to remove gas.
Layered scraping during construction, especially in the case of thick coating, each coating should not be too thick (2 to 3 mm is recommended).
The technique should be smooth and the speed should be moderate when scraping to avoid bubbles due to improper operation.

Adjust environmental conditions
Try to choose a suitable construction environment and avoid operating under high temperature and high humidity conditions.
If necessary, appropriate sunshade or ventilation measures can be taken to prevent water from evaporating too quickly or gas from being trapped.

The application of HPMC in putty powder has significant advantages and can improve the construction performance, surface effect and bonding strength of putty powder, but the addition amount and use method need to be reasonably controlled. The reasons for the foaming of putty powder involve many aspects, including base treatment, material ratio, mixing operation and environmental conditions. By optimizing the formula, standardizing the construction and adjusting the environmental conditions, the bubble problem can be effectively reduced, thereby improving the putty construction effect.