Why do bubbles appear in plastic bottles during production?

In the process of producing plastic bottles, we often have bubbles on the bottle body. What is the reason? Let the small editor of Dalian blow molding product manufacturer analyze it from several aspects.

1、 Process factors:

1. If the speed is too fast, the molten plastic will decompose under the action of large shear 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 of the product is faster than that of the central part. During the cooling process, the plastic edge of the central part shrinks and expands to the outside, making the central part insufficiently filled and forming a vacuum bubble.

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. The back pressure is insufficient. The back pressure controls the speed of the screw backward. When the back pressure is low, the screw backward speed will be faster. It is easy to cause insufficient feed. There is more air in the feed, and it is too late to discharge from the feed inlet, resulting in a large number of bubbles.

2、 Material factor

1. The raw material has moisture.

2. Mold factor.

3. If the mold is trapped, the mold should be maintained or the exhaust slot should be added.

So we must pay attention to these aspects during the production process to make a good bottle.

There are the following reasons for bubbles in plastic products:

1. The raw material contains water, solvent or volatile matter.

2. The plastic temperature is too high or the heating time is too long, resulting in the degradation or decomposition of raw materials.

3. The injection pressure is too low.

4. The holding time is too short.

5. The mold temperature is too low.

6. The injection speed is too fast.

It can be seen from the question that this should be the problem of too fast injection speed, which needs to be solved by exhaust.