The reason and solution of PVC plastic yellowing
When PVC decomposes, dehydrochlorination occurs to form conjugated polyolefin series, which are yellow. Then, what causes the aging and decomposition of PVC, and how can we solve this problem? Next, Lianda Chemical Co., Ltd. will analyze the causes and solutions of PVC yellowing from two aspects of production process and formula.
Technological problems
In the process of extrusion, PVC is heated and sheared by screw and barrel. If the process is not set properly, it will cause decomposition and yellowing of PVC to some extent. The solution is as follows: (1) the yellowing phenomenon can be improved by properly reducing the barrel temperature.
(2) in a proper range, reducing the rotating speed of the main engine and increasing the feed ratio can reduce the shear, make the materials in the screw groove mix more evenly, and make the stabilizer play a full role, so as to reduce the yellowing.
(3) improper start-up method will also cause the product to turn yellow. Restarting the machine may solve this problem.
Formulation problem
Generally appear in the replacement of a batch of additives or manufacturers after the product yellow. The solution is as follows:
(1) increase the content of stabilizer.
(2) adjust the internal and external lubricant balance.
(3) to solve the problem of yellowing, we should supplement the color of pigment or increase the proportion of fluorescent whitening agent.
(4) add UV absorbers to increase the anti-aging effect, lasting protection from fading and yellowing!
