Material Analysis
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EVOH heat-sensitive degradation and discoloration
Problem Phenomenon
EVOH processing >230°C turns yellow-brown with decreased mechanics
Cause Analysis
EVOH vinyl alcohol groups decompose by dealcoholization at high temperature, starting >230°C; excessive residence time aggravates decomposition
Solution
1) Strictly control the upper limit of processing temperature at 190-230°C; 2) Shorten high-temperature residence and increase rotation speed; 3) Add 0.1wt% heat stabilizer; 4) Select low vinyl alcohol content EVOH (ethylene 32-38%) with low decomposition tendency
Key Takeaway
EVOH heat-sensitive decomposition is caused by vinyl alcohol dealcoholization; temperature control is the fundamental countermeasure
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