After some plastic injection molded products (such as polyamide products, especially PA6), they will absorb moisture from the air during storage or use, which will cause the body to expand and deform. It is also very easy to oxidize and change color in high temperature environments, especially during injection The external structure and dimensions are very unstable within a few weeks after molding. Therefore, this type of injection molded product must be subjected to humidity control after molding.
The humidity control treatment method is as follows. Put the plastic products after injection molding and demoulding in hot water or potassium acetate aqueous solution (water/potassium acetate=1/1.25), and the heating temperature is within the range of 100~120℃. The product can not only isolate the air for annealing treatment to prevent oxidation in hot water, but also can make the product reach a moisture absorption balance.
For polyamide injection molded products, after the humidity conditioning treatment, the internal stress generated during the product molding process is eliminated, the crystallinity is improved, and the product structure, shape, and size stabilization process is accelerated. The appropriate amount of water in polyamide products can improve the performance of the products (flexibility, impact strength and tensile strength).
Similarly, after the humidity control treatment (including annealing heat treatment) of the injection molded product reaches the temperature and time required for the heat treatment, attention should be paid to slowly lowering the temperature until it is cooled to room temperature. If the cooling rate is too fast or sudden cooling, it will have a great impact on the performance of the product and generate new internal stress.
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