The reason why there are bubbles in PET cosmetic plastic bottles

In the process of producing PET cosmetic plastic bottles, bubbles often appear in the bottle body. These bubbles will directly lead to unqualified quality control. So what causes the bubbles? Let’s analyze it from several aspects.

First, process factors:

1. The speed is too fast, causing the molten plastic to decompose under the large shearing effect and produce gas.

2. The local cooling of the product is too fast and the shrinkage is uneven. Especially when the wall thickness of the product is large, the surface cooling speed is faster than the center. During the cooling process, the plastic in the center shrinks while expanding to the outside, so that the center is not filled enough and a vacuum bubble is formed.

3. Insufficient pressure and pressure holding make the molten material not close to the cavity surface, which is not conducive to the discharge of air.

4. Insufficient back pressure. The back pressure controls the speed of the screw retreat. When the back pressure is small, the screw retreats quickly, which is easy to cause insufficient feeding. There is more air in the material, and it is too late to be discharged from the feed port, resulting in a large number of bubbles.

Second, material factors

1. The raw material contains moisture.

2. Mold factors

3. The mold is trapped with air, so the mold should be maintained or an exhaust groove should be added.

Therefore, you must pay attention to these aspects during the production process to make a perfect bottle. Yusu Packaging has many years of experience in producing PET injection plastic bottles. With the support of many years of data, Yusu Packaging’s PET plastic bottle qualification rate is more than 99.6% per batch. If you want to produce cosmetic plastic bottles, welcome to consult and conduct on-site factory inspection.