Molds & Tooling
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Yellowing of PEEK Due to Excessive Melt Temperature
Fenómeno do problema
PEEK products turn yellow overall or locally, with color deviating from the natural color family, especially obvious near the gate and at the runner end, accompanied by a slight odor change.
Análise das causas
Melt temperature exceeding the recommended upper limit or too long barrel residence time triggers thermo-oxidative degradation; PEEK has a narrow melt temperature window (usually required to be controlled within 10℃), and discoloration begins as soon as it is over-temperature.
Solução
①Check the actual barrel temperature against the set value zone by zone; ②Shorten the cycle to reduce residence time, and lower the temperature immediately upon shutdown; ③Reduce screw speed and back pressure to decrease shear heat; ④Purge the machine and reheat to verify.
Conclusão principal
PEEK's narrow temperature window requires high precision of the temperature control system; yellowing is an early signal of degradation, and continued production will bring black specks and performance deterioration; temperature verification should use actual measurement rather than the meter display.
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