Attentions For Injection Molding of PET Preforms

PET is called polyterephthalate, currently used in customers is GF-PET. The rheological property of PET in the molten state is better, and the influence of pressure on viscosity is greater than that of temperature. Therefore, the fluidity of melt is mainly changed from pressure.


1. Plastic processing. Because of PET macromolecular contains aliphatic, has certain hydrophilicity and material at high temperature is more sensitive to water, when the moisture content is more than the limit, in the processing of PET molecular weight drops, products with color become fragile. Therefore, must be to dry the material before processing, the drying temperature was 150℃. Generally, the proportion of recycled materials should not exceed 25%, and the recycled materials should be thoroughly dry.


2. The injection molding machine. Because of PET material’s short stable time after melting point and high melting point, so it needs to choose the injection system with less self-friction heat generation when the temperature control section is more plasticized, and the actual weight of the product should not be less than 2/3 of the injection volume of the machine.


3.PET preform mould and gate design . PET preforms are usually moulded by hot runner, there should be heat insulation plate between mould and injection molding machine template, and heat insulation plate must be able to withstand high pressure, and exhaust must be sufficient. So as to avoid local overheating or fracture, but its exhaust depth should not exceed 0.03mm generally, otherwise it is easy to produce flash.


4. Injection rate. Generally, the injection speed should be fast to prevent premature coagulation. But too fast, high shear rate makes the material fragile.


5. Detention time. Do not use excessive residence time to prevent molecular weight degradation.


Under the above precautions, the PET preforms produced have high transparency and good injection molding effects. In addition, the life of the mold will increase. We can not only provide the PET mould, but also provide with the PET injection molding production line – Custom Design Injection Molding Line Set Up.

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