The role of liquid zinc in PVC polymerization.

Liquid zinc, used as a heat stabilizer, can reduce and prevent the formation of structural defects in the PVC backbone, such as unstable structures like dienes, trienes, polyenes with conjugated double bonds, branches, allyl chloride, as well as small molecular structures. It also helps to suppress the decrease in brightness of PVC resin during the stripping and drying processes, thereby improving the thermal aging brightness and thermal stability of the PVC resin. At the same time, liquid zinc also helps to significantly reduce the residual vinyl chloride monomer in PVC resin. Simply add liquid zinc together with vinyl chloride monomer, initiator, and other materials into the polymerization reactor at once.

Reply to 2# zjutmdyu: First of all, thank you for your reply. I’ve read about it in many books, but I want to know why liquid zinc has such an effect; what kind of substance it is, and what chemical reactions take place when it participates in polymerization reactions. Could you help me answer it?

7-9 zinc acid is enclosed within the primary PVC particles during the polymerization process. It can improve thermal stability. Our factory generally uses it only when producing type 8. Because the polymerization temperature of type 8 resin is relatively high.

This post was last edited by wang*neng on 2010-7-1 21:36. Here are my thoughts on adding liquid zinc to composite formulations: 1. The mechanism by which liquid zinc acts as a heat stabilizer is by absorbing hydrogen chloride released during the decomposition of PVC, as hydrogen chloride has a autocatalytic effect on the decomposition of PVC. The unstable structures on the PVC molecular chains did not decrease after the addition of liquid zinc ； 2. Adding liquid zinc has an adverse effect on post-processing, especially for products processed at high temperatures, as it can cause the phenomenon of \"zinc burning\" ； 3. The addition of liquid zinc complicates the polymerization formula system, increasing the number of uncontrollable factors; foreign PVC manufacturers now strive for simpler formulas, with as few additives as possible ； 4. Why are companies still so enthusiastic about this today? Mainly, the addition of liquid zinc can significantly increase the whiteness of PVC products during testing; in my opinion, it is the equivalent of melamine in the PVC industry. The whiteness of domestic products is generally above 80, sometimes even reaching 82 or 84, while that of foreign products is only 76 or 78; their thermal stability during processing is far superior to that of domestic products. What’s the reason?