Injection Molding
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Insufficient Elongation at Break of Polypropylene Injection-Molded Products
Problem Phenomenon
The elongation at break of the product in the tensile test is lower than the standard requirement, and the material behaves brittlely.
Insufficient elongation at break indicates poor material toughness, and brittle fracture easily occurs in actual use.
Cause Analysis
(1) The melt temperature is too low, and the severe molecular chain orientation limits the plastic deformation ability
(2) The mold temperature is too low, and the crystallization is imperfect or uneven
(3) The holding pressure is too high, and the residual stress limits the slippage of molecular chains
(4) Thermal degradation of the material leads to a decrease in molecular weight and a decline in toughness
(5) The product contains defects such as bubbles and impurities that serve as crack sources
Solution
(1) Increase the melt temperature to the higher value within the range of 200-280°C to promote molecular chain relaxation
(2) Increase the mold temperature to the higher value within the range of 40-90°C to improve crystallization
(3) Appropriately reduce the holding pressure to reduce residual stress
(4) Control the barrel temperature to prevent thermal degradation, and avoid long-term high-temperature residence
(5) Ensure the raw material is dry and clean to reduce bubbles and impurities
Key Takeaway
Insufficient elongation at break reflects poor material toughness, and the plastic deformation ability needs to be improved by optimizing temperature parameters and reducing defects.
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