Material Drying
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PET Preform IV Drop (Intrinsic Viscosity Decrease)
Problem Phenomenon
The same batch of resin has decreased blowing strength, and the bottle body is brittle.
Cause Analysis
Hydrolysis and thermal degradation reduce PET intrinsic viscosity (IV); insufficient drying, excessive material temperature, too long residence, and multiple heat histories (recycling) all cause IV drop.
Solution
①Strict drying; ②dual control of material temperature and residence; ③test the IV value of incoming material and preforms; ④evaluate IV of old inventory preforms before use.
Key Takeaway
IV is the general ledger of PET processing quality.
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