Causes of bubbles in plastic bottles

September 05,2021

The plastic bottle is disturbed by gas during the filling process, and some cavities or bubbles are often formed on the surface of the product. Now let's summarize the factors related to the appearance of bubbles.

Process factors:

1. The speed is very fast, so that the molten plastic is decomposed by large shearing, and gas is generated.

2. The part of the product cools very quickly, and the shrinkage is never even. Especially when the wall thickness of the product is relatively large, the surface cooling speed is faster than the center part. During the cooling process, the plastic in the center part shrinks and expands to the outside, making the center Insufficient filling of the part, forming a vacuum bubble.


3. Insufficient pressure and holding pressure make the melt and cavity surface not adhere closely, which is definitely not conducive to the discharge of air.

4. Insufficient back pressure, the back pressure controls the retreating speed of the screw. If the back pressure is relatively small, the retreating speed of the screw will be faster, which is easy to cause insufficient feeding. There is more air in the material, and it is too late to discharge from the feeding port. , Produce a lot of bubbles.

5.Material factors 
The raw material has moisture. Mold Factors The mold is trapped in air, the mold should be maintained or an exhaust groove should be added.