Injection Molding
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Yellowing and embrittlement of PET injection products
Fenómeno do problema
PET injection products appear yellow or yellowish-brown, product brittleness increases, impact strength significantly decreases.
Análise das causas
Processing temperature too high (over 300°C) or material residence time in the barrel too long causes PET thermal degradation and thermo-oxidative degradation, molecular chains break producing colored groups.
Solução
Strictly control barrel temperature 260-290°C, shorten molding cycle, reduce back pressure to 0.3-0.5MPa, check temperature control system accuracy.
Conclusão principal
PET thermal degradation is a common problem in processing; temperature control and residence time management are key.
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