Things to know about preform molds

We should be aware of these products, such as preform molds, blow molding machines, and blow molding molds. Today, what we are introducing here is the knowledge of the product blow molding machine-preforms. If you are also troubled by this problem, Then the following introduction can be helpful to you, let us read it together.

　　The bottle preform of the bottle blowing machine is also called the parison, which is formed by injection of PET pellets. It requires that the proportion of the reclaimed material cannot exceed 10%, and the number of retractions cannot exceed two.

The preform after injection molding or the preform used after heating must be cooled for more than 48 hours, and the used preform cannot be stored for more than 6 months. Different production dates, especially preforms with too long intervals, cannot be mixed. , The primary reason is that the type of raw materials used in the preform, the proportion of the secondary material mixed and the residual stress in the preform are different, and these factors have a significant impact on the molding process of the bottle blowing, and should be treated in detail according to the actual situation. Because PET has strong water absorption, it is necessary to pay special attention to moisture prevention during storage, and it must be dehumidified and dried before processing. The drying conditions are generally 150-180°C for 4 hours, and to prevent the plastic particles from absorbing moisture again, It is necessary to keep the temperature above 140℃. In order to prevent the plastic from turning yellow when shutting down, the desiccant dryer needs to be cooled to 100℃, without dehumidification, only insulation.

In addition, if the material temperature is too high, the screw shear force is too high, or the rotation speed is too fast during PET injection molding, acetaldehyde will simply occur and cause acidification. Generally, the acetaldehyde content of the PET bottle after molding must be less than 3ppm, and the preform will crystallize A certain moisture content is required before, and it is generally required to be about 1000 ppm, at least above 900 ppm, so the preform needs to be placed for a period of time before the moisture content reaches the requirement before it can be crystallized.

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