Processing Machinery
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Degradation from PPO melt temperature out of control
Problem Phenomenon
PPO products show yellowing, embrittlement, and performance decline, especially obvious in batches with excessive barrel temperature or excessive residence time, and the melt flow is abnormal.
Cause Analysis
PPO has high molecular weight and high melt viscosity; excessive residence time at high temperature causes molecular chain scission and degradation; although the thermal stability is good within 300℃, the combination of over-temperature and over-time breaks through the tolerance limit.
Solution
①Control the barrel temperature within the 260~290℃ range; ②shorten the molding cycle to reduce high-temperature residence; ③use a lower melt temperature within the acceptable range; ④purge and replace degraded batches in time.
Key Takeaway
PPO degradation is the cumulative effect of the product of temperature and time; low melt temperature and short cycles are the basic principle for protecting molecular weight; the 300℃ thermal stability boundary cannot be used as a process target.
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