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Precautions for PET bottle preform forming
Oct 19,2022
Precautions for PET bottle preform forming
1. Mold and gate design
PET preforms are generally formed by hot runner molds. There should be a heat shield between the mold and the injection molding machine template, the thickness of which is about 12mm, and the heat shield must be able to withstand high pressure. The exhaust must be sufficient to avoid local overheating or fragmentation, but the depth of the exhaust port is generally not more than 0.03mm, otherwise it is easy to produce flash.
2. Melting temperature
It can be measured by the air injection method in the range of 270-295°C, and can be set at 290-315°C for enhanced GF-PET.
3. Injection speed
Generally, the injection speed should be fast to avoid premature solidification during injection. But too fast, the shear rate is high, the material is brittle, and the injection is usually completed within 4 seconds.
4. Back pressure
The lower the better, so as not to wear out. Generally not more than 100bar, usually do not need to use.
5. Dwell time
Do not use excessive dwell times to prevent molecular weight drop, and try to avoid temperatures above 300°C. If the machine downtime is less than 15 minutes, it only needs to inject air; if it exceeds 15 minutes, it must be cleaned with viscosity PE, and the barrel temperature will drop to PE temperature until it is turned on again.
