How to improve the stability of powder storage

In the application process of powder coatings, especially in the humid and stuffy south, it is common for powder coating users to notice powder agglomeration when opening the box and about to spray.

Usually, after the storage time is exceeded, the powder will exhibit phenomena such as agglomeration and poor flowability, and the coating film will undergo changes such as abnormal gloss, poor leveling, and surface roughness.

We usually believe that there are two reasons for the poor storage stability of powders:

One reason is that powder coatings are kept at high temperatures (close to or greater than the glass transition temperature of the powder) for a long time, causing the powder to transition from a glassy state to a high elastic state, resulting in softening and sticking of the powder. This is manifested as powder agglomeration or aggregation, which is difficult to fluidize and disperse in a fluidized barrel, affecting normal spraying construction.

Another type of special powder coating with reactive extinction agents, extinction curing agents, and other components can increase the activity of the powder.

1. Without affecting the performance of powder coatings and coatings, try to choose resins with high Tg and appropriately increase the amount of pigments and fillers in the formula.

Inorganic substances (such as fillers and inorganic pigments) in powder coatings contribute to the improvement of the final Tg of the powder. It can be seen that the Tg of different types of powder coatings is different, and there are also some differences in the Tg of the same type of powder coatings. Overall, the Tg of sand grain powder is higher than that of flat powder.

2. Based on the performance of different products and customer requirements, choose appropriate acid value and active resins, strictly control the type and dosage of matting agents, and avoid using accelerators.

3. Use other additives sparingly and with caution, communicate with raw material manufacturers to improve the storage stability of raw materials. Most commonly used additives are high molecular weight polymer compounds with lower glass transition temperatures, which can reduce the Tg of powder coatings

4. During powder production, control the particle size distribution, especially to reduce the content of fine powder. The particle size of powder coatings is usually controlled between D50 and 30-40 μ If there are more fine powders below 10um, their specific surface area will rapidly increase, and the contact surface between powders will also increase, making it easy for them to aggregate into clusters. After the powder is ground, wait for the powder in the container to cool before sealing or using cold air in the workshop to prevent the powder from overheating.

5. In the manufacturing process of powder coatings, loose agents such as fumed silica and alumina C with a large specific surface area and strong moisture absorption ability are added externally. Forming an isolation layer between powder coating particles, reducing the chances of collision and agglomeration of powder coating particles, making it less prone to agglomeration, thereby improving the storage stability of powder coating.

For powder coatings used for aluminum profiles, it is recommended that users meet the following conditions during storage and use the powder as quickly as possible:

Storage temperature: not exceeding 30 ℃, preferably below 25 ℃.

Storage environment: Ventilation and dryness should be maintained to prevent direct sunlight on the powder;

The location for storing powder is not allowed to be close to the flame and away from heat sources.

Other precautions: To prevent water accumulation or dripping in the warehouse, powder coating packaging boxes should be placed on shelves or wooden boards isolated from the ground, and the stacking height should preferably not exceed 4 layers.