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At present, most of the bottle blowing process is still a two-step method, that is, the plastic is first made into the bottle embryo, and then the blowing is carried out. The original PET plastic is commonly used.
First, the principle of blowing bottles
At present, the main bottle blowing process can be divided into two parts, namely preheating and blowing two processes.
1. Preheat
The bottle embryo is irradiated by infrared high temperature lamp, and the embryo body part of the bottle embryo is heated and softened. In order to maintain the shape of the bottle mouth, the bottle embryo mouth does not need to be heated, so a certain cooling device is needed to cool it.
2. Blow bottle forming
In this stage, the preheated bottle embryo is placed into the already prepared blowing mold, and the inside is inflated under high pressure to blow the bottle embryo into the required bottle.
Two, the bottle blowing process
The blowing process is a bidirectional stretching process. In this process, the PET chain is bidirectional extension, orientation and arrangement, which increases the mechanical properties of the bottle wall, improves the tensile, tensile and impact strength, and has good air tightness.
Although stretching helps to improve the strength, it should not be over-stretched. The ratio of stretching and blowing should be controlled well: the radial direction should not exceed 3.5 ~ 4.2, the axial direction should not exceed 2.8 ~ 3.1, and the wall thickness of the billet should not exceed 4.5mm.
The blowing bottle is carried out between the glass transition temperature and the crystallization temperature, which is generally controlled between 90 and 120 degrees. In this section, PET shows a high elastic state, and becomes a transparent bottle after rapid blowing, cooling and setting.
