What are the characteristics of PET raw materials What should be paid attention to during injection molding

PET stands for "Polyethylene Terephthalate". It is a saturated polyester formed by polymerizing terephthalic acid and ethylene glycol. It has good transparency, gloss and gas barrier properties, and is in line with food Safety standards, and can be recycled for reuse. The glass transition temperature (Tg) of PET is between 75-80°C, the injection molding temperature is about 270-310°C, and the mold temperature is about 130-150°C. Due to the strong water absorption of PET, special attention must be paid to moisture-proof during storage, and it must be dehumidified and dried before processing. The drying condition is usually 4 hours at 150-180°C, and in order to prevent the plastic pellets from absorbing moisture again, must Keep warm at a temperature above 140°C. In order to prevent the plastic from turning yellow when shutting down, the dehumidification dryer needs to be cooled to 100°C. No dehumidification but only heat preservation. In addition, if the material temperature is too high, the shear force of the screw is too high or the rotation speed is too fast during PET injection molding, acetaldehyde will easily be produced and cause acidification. Usually, the acetaldehyde content of the PET bottle after molding must be less than 3ppm.