The preform of the blow molding machine is also called a parison. The PET pellets are injection-molded. It requires that the proportion of recycled materials should not exceed 10% and the number of recovery should not exceed two.

The preform after injection molding or the preform used after heating must be cooled for more than 48 hours, and the storage time of the used preform can not exceed 6 months. Different production dates, especially the long interval of the preform can not be mixed, first The reason is caused by the type of material used in the preform, the proportion of the secondary material mixed in and the residual stress in the preform, and these factors have a significant impact on the molding process of the blowing bottle, and should be treated in detail according to the actual situation. Since PET has a strong water absorption property, it is necessary to pay special attention to moisture prevention during storage, and it is necessary to dehumidify and dry before use, and the dry condition is usually carried out at 150 to 180 ° C for 4 hours, and to prevent the plastic particles from absorbing moisture again, It is necessary to keep warm at a temperature above 140 ° C. To prevent the plastic from turning yellow when the machine is stopped, the dehumidifying and drying machine needs to be cooled to 100 ° C, and the heat is not dehumidified.

In addition, if the material temperature is too high, the shearing force of the screw is too high, or the rotation speed is too fast, the acetaldehyde is likely to be acidified during injection molding. Usually, the acetaldehyde content of the PET bottle after molding is less than 3 ppm, and the preform is crystallized. The pre-required moisture content is generally required to be around 1000 ppm, and at least 900 ppm or more. Therefore, the preform can be crystallized after the injection temperature is required for a certain period of time.