Injection Molding
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Insufficient elongation at break of low density polyethylene injection products
Problem Phenomenon
The elongation at break of the product in tensile testing is lower than the standard requirement, and the material behaves brittle.
Insufficient elongation at break indicates poor material toughness, and brittle fracture easily occurs in actual use.
Cause Analysis
(1) Melt temperature too low; severe molecular chain orientation limits plastic deformation ability
(2) Mold temperature too low; incomplete or uneven crystallization
(3) Holding pressure too high; residual stress limits molecular chain slippage
(4) Material thermal degradation reduces molecular weight, toughness decreases
(5) The product contains bubbles, impurities and other defects as crack sources
Solution
(1) Increase melt temperature to the higher value within the 160-220°C range, promote molecular chain relaxation
(2) Increase mold temperature to the higher value within the 30-60°C range, improve crystallization
(3) Appropriately reduce holding pressure, reduce residual stress
(4) Control barrel temperature to prevent thermal degradation, avoid prolonged high-temperature residence
(5) Ensure raw material is dry and clean, reduce bubbles and impurities
Key Takeaway
Insufficient elongation at break reflects poor material toughness; plastic deformation ability needs to be improved by optimizing temperature parameters and reducing defects.
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