It often takes a period of time for paint products to be used from production to use, which may be long or short. Satisfactory coating products should not change in quality when stored in the container, and when the container is opened for construction, it should be the same as when the product was just produced. However, due to different types of coatings, different levels of production control, or poor storage and storage, the physical properties of the product in the container often change, which may seriously affect the use, especially the oxidation-drying coatings are most likely to change. Therefore, general coatings have a shelf life. In terms of production , the shelf life of the product should be extended as much as possible. When using it, you should first check whether the storage time of the paint product in the original container has expired, and its original state. When purchasing a batch of paint products, in order to ensure that there are no problems during use, samples should be taken to check the state of the product in the container, and a test of storage under specific conditions should be carried out to check the change that is, the storage stability. examine. Storage stability should also be used as a necessary performance control item in the process of coating design and production.
Checking of the condition in the container is usually done during the paint sampling process. When sampling, first check whether the container is complete. The interval between the production date of the mark and the sampling inspection date should be clearly recorded. Check whether the seal is complete and tight, and then open the cover after making a record. The items to be checked for liquid paints are: crusting, delamination, whether there is liquid or pigment floating in the paint, and inserting a wooden or metal stick or glass rod into the container to check whether there is precipitation and agglomeration, and whether the precipitation is easy Stir, after stirring, whether it is uniform, whether the color is consistent from top to bottom, etc. Keep records of inspections. After checking the status in the container , stir again and take a representative sample. The testing methods listed in the JIS standard of Japan are available for reference.
Storage stability refers to the degree to which the physical or chemical properties of the product or the resistance of the coating product within the specified The degree of change in properties that may occur after storage under these conditions . For the detection of storage stability, CHINA has formulated the national standard GB/T 6753. 3-1986 "Test Method for Storage Stability of Paint". According to this standard, the conditions for determination are divided into two types: natural environment storage and storage under accelerated conditions of 50C±2C. Take 3 parts of the sample to be tested and put them in standard gland-type metal paint cans with a volume of 0.4L , 1 can of the original sample is inspected before storage, and 2 cans are subjected to storage test. The items checked are:
①The inspection of skinning, corrosion and putrefaction smell is divided into 6 grades of 0, 2, 4, 6, 8 and 10;
② The inspection of the settlement degree shall also be evaluated according to the above 6 grades;
③ The inspection of coating particles, rubber blocks and brush marks shall also be evaluated according to the above 6 grades;
④ Check the viscosity change, compare the stored viscosity with the original viscosity, and evaluate according to the ratio and percentage according to 6 grades.
Finally, take "pass" or "fail" as the conclusive evaluation, or evaluate according to product requirements. According to the requirements of product varieties, there are different storage stability testing methods for different varieties, such as the testing method for sedimentation of road line drawing paint during storage specified in ASTM D1309-1993 (2004).
