In the field of coating applications, high build primer is a common and important product. The main function of high build primer is to provide a solid and smooth foundation for the final topcoat, which can effectively fill the tiny unevenness on the surface, increase the adhesion of the coating, and improve the uniformity and durability of the final coating effect.
As a high-performance primer, many consumers often face a question after purchase: How long can high build primer be kept after opening? This article will answer this question in detail, explore the various factors that affect the shelf life of primers, and propose suggestions on how to extend its shelf life.
How long is the shelf life of high build primer after opening?
High build primer generally has a clear shelf life label when it is unopened, usually 12 to 24 months, depending on the composition and production process of the primer. This shelf life refers to the period during which the product can maintain its performance under optimal storage conditions.
Once opened, the storage conditions of high build primer will change, and the chemical components in it will begin to react after contact with air, which may affect its quality. Therefore, the shelf life of the primer after opening is closely related to the storage environment, but it is usually significantly shortened, about 6 months to 1 year. If the primer is not stored properly, the shelf life may be further shortened, and it may even be unusable within a few weeks.
What are the factors that affect the shelf life of high build primer after opening?
How long a high build primer can be kept after opening depends on several factors. Understanding these factors can help to properly store the primer after using it and extend its service life.
1. Chemical composition of primers
Different types of high build primers differ in their chemical composition, some products are solvent-based, and some are water-based formulas. Solvent-based high build primers are more stable than water-based primers and can be stored longer after opening because the solvent evaporates relatively slowly. Water-based high build primers are more sensitive to environmental changes, and water evaporation can cause the primer to deteriorate, and its shelf life is usually shorter than that of solvent-based primers.
In addition, polyurethane or epoxy resin high build primers usually contain two or three components and need to be mixed before use. Once the components are mixed, the primer is usually usable for a few hours to a day. Therefore, unmixed single components will last longer than mixed components.
2. Storage temperature
Temperature is one of the key factors affecting the shelf life of high build primer. After opening, the primer should be stored in a dry, cool place, away from direct sunlight and extreme temperature fluctuations. The ideal storage temperature is 5℃ to 25℃. If the temperature is too high, the evaporation of solvents or water will accelerate, causing the primer to dry or deteriorate prematurely; while in an extremely low temperature environment, some components may crystallize or solidify, affecting its performance.
During storage, continuous temperature stability is also important. If the temperature changes frequently, the chemical composition of the primer may change, accelerating aging and shortening the shelf life.
3. Sealing
Sealing is another important factor that determines the shelf life of high build primer. After each use of primer, you must ensure that the container is tightly sealed. If the container is not tightly sealed, oxygen and moisture in the air will enter the container, which will accelerate the oxidation and volatilization of the primer, causing it to dry and harden, making it unusable.
When sealing, it is recommended to clean the residual paint on the edge of the container to ensure that the lid can be completely sealed. In addition, before closing the container, you can add a layer of plastic film to cover the mouth of the can to enhance the sealing effect and reduce the chance of air entering.
4. Container size and remaining amount
If the high build primer is not used up after opening, the less the remaining amount, the shorter the shelf life. This is because the larger the proportion of air in the container, the wider the area of the primer exposed to oxygen, and the faster the oxidation rate. If possible, transfer the remaining primer to a smaller container to reduce the air content in the container, which can effectively extend the shelf life of the primer.
How to judge whether the high build primer can still be used after opening?
Even if it is stored strictly in accordance with the storage requirements, the performance of the high build primer after opening may still decline after long-term storage. So, how to judge whether these primers can continue to be used? The following points can be used as a basis for judgment:
1. Appearance changes
If the color of the high build primer changes significantly after opening, or a thick hard shell appears on the surface of the primer, this usually indicates that the primer has been oxidized or other chemical reactions have occurred and is no longer suitable for use. In addition, if there are lumps, flocs or a significant increase in viscosity inside the primer, it also indicates that its chemical properties have changed, affecting its coating and performance.
2. Odor changes
High build primer usually has a specific smell, which is caused by the volatilization of solvents and chemical components. If the smell becomes pungent or has a noticeable sour smell after opening the container, it means that the primer may have deteriorated. After the solvent components of the primer stored for a long time decompose, the smell will no longer be as fresh as new paint, which is also a way to judge whether it has deteriorated.
3. Fluidity changes
Normal high build primer should have good fluidity and be easy to apply. If the primer becomes abnormally viscous after opening and is difficult to apply evenly, it means that the solvent or water in the primer has evaporated in large quantities and lost its due performance. At this time, even if it is used forcibly, the coating effect is difficult to achieve the expected effect.
4. Poor coating effect
During use, if you find that the drying time after the primer is applied is prolonged, or the coating is uneven, bubbling, falling off, etc., it is likely that the primer has failed and can no longer provide the original protection and adhesion. If the high build primer has deteriorated, even if it is used forcibly, the coating quality cannot be guaranteed, and it may also bring subsequent repair work.
How to extend the shelf life of high build primer after opening?
Although the shelf life of high build primer after opening will be significantly shortened, its service life can be effectively extended by taking appropriate measures. Here are some practical suggestions:
1. Sealed container
Make sure to seal the container immediately after each use to prevent air and moisture from entering. Clean the residual paint on the edge of the container and ensure that the lid is tightly sealed. In addition, using plastic film or sealing tape to further strengthen the sealing effect can reduce the entry of air.
2. Store in a cool and dry place
Store the primer after opening in a dry, cool, well-ventilated place, away from direct sunlight and extreme temperature fluctuations. The ideal storage temperature is 5℃ to 25℃, and avoid frequent temperature changes.
3. Use smaller containers
If there is not much high build primer left, you can transfer it to a smaller container to reduce the proportion of air in the container, thereby delaying the oxidation process of the primer.
4. Avoid frequent opening
After each use of high build primer, try to reduce the number of frequent openings. Frequent openings will increase the chance of the primer coming into contact with the air, accelerating its oxidation and volatilization. Therefore, rationally planning the usage and using a larger amount at one time can reduce the number of times the primer is opened.
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