Why Do PET Plastic Bottles Bubble

We often have bubbles in the bottle body in the process of producing PET plastic bottles. What is the reason? Let's analyze it from several aspects.

First, process factors:

1, the speed is too fast, so that the molten plastic by large shear action and decomposition, gas generation.

2, the partial cooling of the product is too fast and the contraction is uneven, especially when the wall thickness of the product is large, the surface cooling speed is faster than the central part. In the cooling process, the plastic in the central part shrinks while expanding to the surface, so that the central part is not filled enough, forming a vacuum bubble.

3, insufficient pressure and pressure holding, so that the fusion and cavity surface is not close, is not conducive to the discharge of air.

4, insufficient back pressure, back pressure control screw back speed, back pressure is small, screw back speed will be fast, easy to produce insufficient feed, the air into the material is more, too late to discharge from the feed port, produce a large number of bubbles.

Second, material factors

1. Moisture in raw materials.

2. Mold factors

3. If the mold is trapped in air, the mold should be maintained or an exhaust groove should be added.

So you must pay attention to these aspects in the process of making a perfect bottle.