Why does brittle fracture of plastic products occur?

Brittle fracture is a common and complex problem in the manufacture of plastic products. So, what factors typically lead to this phenomenon? Engineers at Yize Mould, who have 15 years of extensive experience in moldmaking, have summarized the following potential causes of brittle fracture:

1. Insufficient injection and holding pressure on the mold from the injection press;
2. Back pressure too low, resulting in friable raw material;
3. Back pressure too high, causing increased shear and friction heat;
4. Injection rate too slow, preventing full crystallization of material;
5. Mold temperature too high, causing overheating, decomposition or degeneration of raw materials;
6. Mold temperature too low to prevent full crystallization;
7. Insufficient injection and holding time;
8. Prolonged idle time of the injection molding press or a long molding cycle;
9. Long shelf life of the material;
10. High proportion of recycled material in new material;
11. Insufficient strength, elasticity or viscosity of the raw material;
12. Improper use or excessive addition of additives;
13. Incomplete drying of raw materials;
14. Uneven internal structure of the product, with some areas too thick and others too thin, and improper feed design;
15. Uneven mold feed and insufficient cold grooves;
16. The walls of the product are too thin;
17. Unstable and fluctuating injection molding press temperature;
18. Poor cleaning of the material channel in the injection molding press;
19. Improper ejection design resulting in increased stress in the plastic and subsequent failure;
20. Poor design of the cooling system in the plastic mold.

The above factors can potentially lead to brittle fracture of plastic products. However, in actual production conditions, the situation can be more complex and variable, requiring specific analysis of each problem based on the extensive experience of the personnel involved.