Polypropylene Homopolymer and Copolymer Impact Performance Differences
Polypropylene impact copolymers sacrifice flexural modulus to gain sub-zero toughness through dispersed ethylene-propylene rubber domains in an isotactic matrix.
Izod Impact Strength
Meaning
Quantitative measure represents the amount of energy absorbed per unit area during the fracture of a plastic specimen under high-speed impact. This value is fundamental for assessing the toughness of a resin and its suitability for structural applications. Izod impact strength remains one of the most widely cited mechanical properties in the plastics industry.
Energy Calculation
Weighted pendulums strike a clamped bar and continue to a certain height. The difference between the initial and final heights determines the work performed on the specimen.
Notch Sensitivity
Polymer chains respond differently to sudden loads when a surface defect or sharp corner is present. Cutting a standardized notch into the specimen concentrates stress and reveals how the material might behave around holes or ribs in a moulded part. Izod impact strength varies greatly depending on whether the test is conducted on notched or unnotched samples.
Quality Control
Moulders use this metric to verify that processing conditions have not degraded the polymer during production. Excessive melt temperature or high shear can break down molecular chains and lead to a drop in izod impact strength compared to the virgin resin. Regular testing helps maintain the safety and reliability of finished components.