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Analysis of the specific causes of plastic bottles

Carrie Mar 13,2019 Share this post:

Generally speaking, the fragile plastic bottles are mainly caused by five aspects: mold, equipment, raw materials, process and product design.

First, plastic bottle mould

1. If the gate is too small, consider adjusting the gate size or adding an auxiliary gate.

2. If the runner is too small or improperly configured, it should be balanced as much as possible or the size of the runner should be increased.

3. Poor mold structure causes abnormal injection cycle.

vaccine bottle

Second, equipment aspects

1. There are dead corners or obstacles in the barrel, which can easily promote the degradation of the melt.

2. The plasticizing capacity of the machine is too small, the plastic is not plasticized in the barrel; the plasticizing capacity of the machine is too large, the plastic is heated and sheared for too long in the barrel, the plastic is easy to age, and the product becomes brittle. .

3. The ejector unit is inclined or unbalanced, and the top dry cross-sectional area is small or improperly distributed.

twin neck bottle

Third, Raw materials

1. When the raw materials are mixed with other impurities or doped with an inappropriate or excessive amount of solvent or other additives.

2. Some plastics, such as ABS, will undergo catalytic cracking reaction with water vapor when heated under damp conditions, causing large strain on the part.

3. If the number of plastic regenerations is too high or the content of recycled materials is too high, or the heating time in the barrel is too long, the parts will be brittle.

Fourth, the quality of the plastic itself is not good, for example, the molecular weight distribution is large, the composition of the uneven structure containing rigid molecular chains is too large; or it is contaminated by other plastics, contaminated with bad additives, and contaminated with dust impurities, which is also the cause of brittleness. 


1. The temperature of the barrel and nozzle is too low, and it is raised. If the material is easily degraded, the temperature of the barrel and nozzle should be increased.

2. Reduce the pre-plastic back pressure and speed of the screw to make the material slightly loose and reduce the degradation of the plastic due to shearing and overheating.

3. The mold temperature is too high, the demoulding is difficult; the mold temperature is too low, the plastic is prematurely cooled, the fusion joint is poorly fused, and cracking is easy, especially for high melting point plastics such as polycarbonate.

4. The cavity core should have a proper draft angle. When the core is difficult to demould, it is necessary to increase the cavity temperature and shorten the cooling time; when the cavity is difficult to remove, the cavity temperature should be lowered and the cooling time should be prolonged.

5. Minimize the use of metal inserts, brittle hot and cold plastics such as polystyrene, and can not be added to the insert injection molding.

Fifth, product design

1. The product has sharp corners, notches or areas with large differences in thickness which are prone to stress cracking.

2. The product design is too thin or too hollow.

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