Material factors
1. Raw materials contain moisture
2. Mold factor
3. The mold is trapped in the air, so the mold should be maintained or an exhaust slot should be added
Therefore, we must pay attention to these aspects in the production process in order to make beautiful bottles.
Technical factors
1. The speed is too fast, so the molten plastic is decomposed under the action of large shear, and gas is generated.
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 rate is faster than that of the central part. During the cooling process, the plastic in the center part shrinks and expands outward, making the center part insufficiently filled and forming a vacuum bubble.
3. Insufficient pressure and holding pressure make the melt not close to the surface of the cavity, which is not conducive to exhausting.
4. Insufficient backpressure, control the backward speed of the screw rod. When the backpressure is small, the screw retreats faster, which easily leads to insufficient feed. There is a lot of air brought into the material, and it is too late to be discharged from the feed port, resulting in a large number of air bubbles.

Production method
There are many ways to make polyethylene, the common ones are the polymerization of ethylene at 200-300 and 1000-2000 atmospheres, in polyethylene, no other substances are doped. The polyethylene prepared by this method has low density, soft quality, and high stability to sunlight, air, moisture, and chemical agents, so there is no need to add stabilizers and plasticizers, which are mostly toxic or highly toxic.
Features: plastic bottles are easy to carry, not itchy, acid and acid resistant, easy to produce, easy to recycle.