Izod Impact (Unnotched) ASTM D4812

Impact resistance of polymers using pendulum impact- Izod Impact Testing (Unnotched Izod) ASTM D4812, ISO 180

The Unnotched Izod Impact test is a single point test that measures a material's resistance to impact from a swinging pendulum. It is defined as the kinetic energy needed to initiate and continue a fracture until the specimen is broken. This test can be used as a quick and easy quality control check to determine if a material meets specific impact properties or to compare materials for general toughness.

The test procedure involves clamping the specimen into the pendulum impact test fixture with the thin edge facing the striking edge of the pendulum. The pendulum is then released and allowed to strike through the specimen. If breakage does not occur, a heavier hammer is used until failure occurs.

The standard specimen size for ASTM is 64 x 12.7 x 3.2 mm (2½ x ½ x 1/8 inch), with the most common specimen thickness being 3.2 mm (0.125 inch). However, the preferred thickness is 6.4 mm (0.25 inch) because it is less likely to bend or crush. The standard specimen for ISO is a Type 1A multipurpose specimen with the end tabs cut off, resulting in a test sample measuring 80 x 10 x 4 mm.

ASTM impact energy is expressed in J/m or ft-lb/in, while ISO impact strength is expressed in kJ/m2. To calculate impact strength, the impact energy is divided by the thickness of the specimen for ASTM, or by the area under the notch for ISO. The test result is typically the average of 5 specimens for ASTM and 10 specimens for ISO.

The higher the resulting numbers, the tougher the material. Therefore, the Unnotched Izod Impact test is an important tool for materials scientists and engineers to assess the impact properties of different materials. This information can be used to inform material selection, design, and quality control in various industries, including automotive, construction, and aerospace.