How to solve stress cracking of PBT plastic during injection molding

Polybutylene terephthalate (PBT) is a thermoplastic with excellent properties and is widely used in the field of injection molding. Its excellent mechanical properties, heat resistance and electrical properties make it an ideal choice for a variety of industrial applications. However, during the injection molding process, PBT plastics may face the problem of stress cracking, which not only affects the appearance quality of the product, but may also lead to a serious decline in its performance and service life.

Analysis of the causes of stress cracking
Internal residual stress: During the injection molding process, due to the rapid cooling and solidification of the molten material, combined with the unreasonable mold design and process parameters, residual stress may be generated inside the product. These residual stresses are very likely to cause cracking during subsequent processing or use, especially when subjected to external stress or temperature changes.
External stress concentration: Defects in product design, such as sharp corners, uneven wall thickness or poor bonding between metal inserts and plastics, may lead to stress concentration, thereby significantly increasing the risk of cracking.
Raw material quality issues: Factors such as impurities in the raw materials, excessive moisture content or uneven molecular weight distribution will have a negative impact on the stress cracking performance of PBT plastics.
Environmental factors: The ambient temperature and humidity during the injection molding process and the contact with chemicals during the subsequent processing may affect the stress cracking performance of PBT plastics.

Solutions for stress cracking
Optimize product design: During the product design stage, sharp corners and structures with uneven wall thickness should be avoided to reduce stress concentration. At the same time, the combination of metal inserts and plastics should be reasonably designed, such as using preheated inserts, increasing plastic thickness or optimizing insert shapes, so as to improve the bonding strength and reduce the risk of stress cracking.
Adjust injection molding process parameters: The optimization of process parameters is crucial. By adjusting parameters such as injection pressure, speed and holding time, internal residual stress can be effectively reduced. In addition, increasing the mold temperature helps to improve the fluidity of the melt and reduce the residual stress caused by uneven cooling. At the same time, extend the cooling time to ensure that the product is fully solidified before demolding to reduce the stress caused by temperature changes.
Improve the quality of raw materials: It is crucial to select PBT plastic raw materials with stable quality and uniform molecular weight distribution. Fully dry the raw materials to ensure that the moisture content is lower than the standard requirements, and avoid using raw materials containing impurities or recycled materials to reduce the risk of stress cracking.
Improve the injection molding environment: Control the ambient temperature and humidity of the injection molding workshop to ensure that the injection molding process is carried out under stable conditions, which helps to improve product quality. In addition, regularly clean the injection molding machine and mold to avoid impurities and contaminants affecting the overall quality of the product.
Use advanced injection molding technology: Introduce mold flow analysis software to simulate and optimize the injection molding process, which can effectively predict the stress distribution of the product and provide guidance for mold design and process parameter setting. At the same time, the use of advanced injection molding machine control systems to achieve precise control of injection pressure, speed, holding time and cooling time can significantly reduce the generation of internal residual stress.