With the improvement of living standards, people's awareness of green environmental protection is increasing. Powder coatings, with their advantages of high efficiency, environmental friendliness, and economy, have achieved rapid development.
Powder coatings require storage in a well-ventilated, dry, and clean environment below 30℃. They must not be placed near fire sources or heating, and direct sunlight should be avoided. During transportation, the product must be protected from rain or direct sunlight.
Humid environments and excessively high temperatures can easily cause powder coatings to clump during manufacturing, storage, transportation, and use, leading to clogging and empty spray guns during powder coating, thus seriously affecting the powder application rate and the smoothness of the coating surface. So how should powder coatings be stored?
1. If actual conditions permit, to ensure the performance stability of powder coatings, it is recommended to store them in an environment that meets specific standards: the ambient temperature should be controlled at ≤30℃, and the relative humidity should be ≤60%. It should be noted that some special types of powder coatings (such as transparent powder) have even stricter requirements for the storage environment, usually requiring the ambient temperature to be controlled below 25℃. If the storage warehouse lacks temperature and humidity control equipment, powder coatings should be stored in a cool, well-ventilated area. Direct sunlight must be avoided, and the area should be kept away from sources of heat such as fire and heating equipment, as well as high-humidity environments such as water tanks and damp corners, to prevent damage to the coating's performance.
2. The particle size of powder coatings is a key factor affecting their storage stability. An unreasonable particle size distribution can easily lead to problems such as clumping and decreased flowability during storage. Taking into account factors such as production cost (excessively fine particle size increases grinding energy consumption), storage stability (both excessively coarse and fine particle sizes may affect stability), coating leveling properties (appropriate particle size helps improve coating smoothness), and powder application rate (reasonable particle size improves electrostatic adsorption efficiency), the optimal particle size range for ordinary planar powder coatings is as follows: powder particles smaller than 10μm account for less than 10% of the total volume, powder particles smaller than 40μm account for 45%~50% of the total volume, and powder particles smaller than 80μm account for more than 90% of the total volume. For powder coatings with special decorative effects (such as hammered or sanded textures), the particle size range can be adjusted appropriately according to specific performance requirements.
3. In the grinding and sieving process of powder coating flakes, the coating performance can be optimized by adding an appropriate amount of loosening agent. Loosening agents effectively reduce the angle of repose of powder coatings (a smaller angle of repose results in better powder flowability), reducing the probability of powder agglomeration during storage. Furthermore, adding loosening agents can regulate the affinity and cohesion between film-forming molecules in the powder coating, thereby increasing the anti-caking temperature of the coating, significantly improving its storage stability, and enhancing the flowability of the dry powder for easier subsequent application. It is important to note that during electrostatic powder coating, loosening agents can reduce the risk of powder clogging the spray gun and prevent agglomeration and sticking to the coating walls. However, the maximum amount of loosening agent added should not exceed 0.05%. Excessive addition can affect the coating's sprayability (e.g., reducing electrostatic adsorption) and may also lead to defects such as pinholes and craters on the coating surface, affecting the appearance quality.
4. In the powder coating production process, the sieved powder generates frictional heat during grinding and sieving. Therefore, it is not advisable to package it immediately after sieving. If packaged while still warm, the powder is prone to condensation due to temperature changes inside the sealed bag, leading to moisture absorption and clumping. Therefore, it is recommended to spread the sieved powder evenly and allow it to cool naturally to room temperature before packaging. Simultaneously, when storing powder coatings, avoid placing them in areas susceptible to contamination by water, organic solvents (such as alcohol and acetone), oils, and other impurities to prevent contamination and affect performance. Furthermore, after opening and using powder coatings, do not expose the remaining portion to air; promptly reseal or tightly seal the packaging bag to prevent dust and debris from entering and ensure coating purity.
5. During the powder coating formulation design stage, if the selected resin has minimal impact on other key coating properties (such as adhesion, impact resistance, and corrosion resistance), it is recommended to prioritize resins with higher glass transition temperatures. Resins with higher glass transition temperatures exhibit slower molecular movement at room temperature, reducing the likelihood of adhesion and effectively minimizing clumping during storage, thus improving storage stability and extending shelf life.
