Injection Molding
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Insufficient Rigidity of Block Copolymer Polypropylene Injection Molded Products
Problem Phenomenon
The product has a large deformation when stressed, and the rigidity modulus is lower than the design requirement.
Insufficient rigidity causes excessive deformation of the product in use, affecting function and safety, and is especially critical in structural parts.
Cause Analysis
（1）The crystallinity of block copolymer polypropylene is low, and the rigidity modulus is insufficient
（2）The product wall thickness is too thin or the reinforcing rib design is unreasonable
（3）The mold temperature is low, the cooling is too fast, and the crystallization is insufficient
（4）The barrel temperature is high, the material degrades, and the molecular weight decreases
（5）The material grade is improperly selected or the reinforcing material is insufficiently added
Solution
（1）Increase the mold temperature to a higher value within the 40-90°C range to increase the crystallinity
（2）Optimize the product design, increase the wall thickness or reinforcing ribs, and increase the section moment of inertia
（3）Control the barrel temperature at a reasonable value within the 200-270°C range
（4）Extend the cooling time to ensure sufficient crystallization
（5）Select a high-rigidity grade or add a nucleating agent, and use reinforcing materials when necessary
Key Takeaway
Insufficient rigidity is caused by low crystallinity or unreasonable structural design, and needs to be solved from both process parameters and product design.
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