Molding Process
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PVC De-HCl Degradation Mechanism
Problem Phenomenon
Products turn from yellow to brown then black, accompanied by pungent odor; once degradation occurs it spreads rapidly
Cause Analysis
C-Cl bond in PVC molecule is weak, dehydrochlorination zipper-style when heated: once one chlorine is removed, an allyl chloride site forms which is more unstable, chain removal of HCl; released HCl autocatalytically accelerates degradation
Solution
①Once degradation occurs, immediately stop and replace barrel; ②Heat stabilizer formula is the first line of defense against degradation; ③Dual control of temperature and residence time; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
PVC degradation is an autocatalytic chain reaction; once started it is irreversible and spreads with acceleration, prevention is the only effective strategy; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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