Why do plastic products age and become brittle?


1. Mold (1) The gate is too small, you should consider […]

1. Mold

(1) The gate is too small, you should consider adjusting the gate size or adding an auxiliary gate.

(2) If the runner is too small or the configuration is improper, it should be arranged as balanced as possible or increase the size of the runner.

(3) Poor mold structure causes abnormal injection cycle. 

2. Equipment

(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, and the plastic is not fully plasticized in the barrel; the plasticizing capacity of the machine is too large, and the time for the plastic to be heated and sheared in the barrel is too long, the plastic is easy to age, and the product is changed. brittle.

(3) The ejector device is tilted or unbalanced, and the ejector cross-sectional area is small or improperly distributed.


3.raw materials

(1) When the raw materials are mixed with other impurities or doped with inappropriate or excessive solvents or other additives.

(2) Some plastics, such as ABS, will react with water vapor when heated under damp conditions, causing large strains on the parts.

(3) Too many times of plastic recycling or too high content of recycled materials, or too long heating time in the barrel will promote the embrittlement of the parts.

(4) The quality of the plastic itself is not good, for example, the molecular weight distribution is large, and the components with uneven structure such as rigid molecular chains occupy too much; or it is contaminated by other plastics adulteration, bad additives, dust and impurities, etc., which can also cause brittleness. the reason. 

4. the process

(1) The temperature of the barrel and nozzle is too low, increase it. If the material is easy to degrade, the temperature of the barrel and nozzle should be increased.

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

(3) Mold temperature is too high, demolding is difficult; mold temperature is too low, the plastic is cooled prematurely, the weld seam is poorly fused, and it is easy to crack, especially for high-melting plastics such as polycarbonate.

(4) The cavity and core must have a proper demoulding inclination. When the core is difficult to demold, increase the cavity temperature and shorten the cooling time; when the cavity is difficult to remove, reduce the cavity temperature and extend the cooling time.

(5) Use metal inserts as little as possible. Brittle plastics with a large heat and cold specific capacity, such as polystyrene, should not be used for insert injection molding.


5. product design

(1) The product has sharp corners, gaps or parts with large differences in thickness that are prone to stress cracking.

(2) The product design is too thin or too much hollow.More about:plastic sport water bottle

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