ISO 179 is an international standard used to determine the Charpy impact strength of rigid plastics. It specifies test procedures, sample preparation, and reporting methods, providing a consistent way to measure and compare the impact resistance of various plastic materials for quality control and material selection.
Overview of ISO 179
ISO 179 is an internationally recognized standard developed by the International Organization for Standardization, specifically focusing on determining the Charpy impact strength of plastics. The standard outlines the method for assessing the ability of rigid plastics to withstand sudden impacts, providing a reliable numerical value for comparison and quality control. ISO 179 specifies the procedure, apparatus, and sample requirements necessary to perform Charpy impact tests, helping manufacturers and laboratories evaluate how different plastic materials behave under defined impact conditions.
Test application and materials tested
This standard is primarily used for rigid thermoplastic and thermosetting materials, including both notched and unnotched specimens, to assess their impact resistance. The procedure helps to determine the brittleness, strength, and toughness of molded or extruded plastic products. Test results are commonly utilized in product development, manufacturing quality control, and material specification compliance across industries such as automotive, construction, and packaging. Following these standardized methods ensures that results are measured consistently and can be compared directly between different materials or production lots.
Benefits of using ISO 179
The implementation of ISO 179 offers several advantages for producers and researchers working with plastics. The protocol provides a common benchmark for impact resistance, enabling transparent material selection and performance assessment. It is also widely referenced in supplier and customer agreements to verify that products meet minimum criteria, making it integral to supplier certification and regulatory compliance. Its use lays the foundation for further material development, process optimization, and troubleshooting.
Takeaway
ISO 179 plays a key role in the standardized testing of the impact strength of plastics. Its methodology supports consistent data and comparability across projects, suppliers, and industries, making it an essential reference for anyone involved in the testing or specification of rigid polymer materials.
Preparation of test specimens
For ISO 179 testing, samples must be prepared according to the specified thickness, width, and length outlined in the standard. The plastic specimens are often notched prior to testing, as notched bars provide more consistent and meaningful results for materials likely to experience brittle fracture. Accurate preparation and conditioning of these samples are critical to ensure the validity of the test data. Specimens are typically stored at standard temperature and humidity for a minimum of 16 hours before testing to normalize their physical condition.
Setting up the testing apparatus
The Charpy testing machine must be calibrated and checked for compliance with ISO 179 requirements. The pendulum or striker should have sufficient energy for breaking the specimens and must be set to the appropriate starting position. The test support and anvil spacing are adjusted to match those described in the standard. Environmental conditions, such as temperature and humidity, are noted as they may affect results.
Executing the test and recording results
Tilt the specimen so the notched side faces the striker, resting it horizontally on supports with the notch centered. Release the pendulum to strike the specimen and break it in a single motion. After each test, the energy absorbed by the sample is measured and recorded. Multiple specimens are tested to acquire statistically valid data; ISO 179 typically requires a minimum of five specimens per sample. Results are reported as kilojoules per square meter (kJ/m²), providing a quantitative value for comparing the material’s resistance to Charpy impact.
Key considerations
The accuracy of ISO 179 results depends on precise sample preparation, consistent testing conditions, and proper machine calibration. Environmental influence should be minimized or noted for repeatability. Documenting test parameters thoroughly aids in reproducibility and data analysis.
Test data interpretation
Interpreting ISO 179 results involves comparing the absorbed energy values. Higher values indicate tougher or more impact-resistant plastics. Any abnormal fracture behavior or unexpected results should be documented and may require additional analysis or retesting to confirm findings.
Summary
The ISO 179 Charpy impact test offers a clear, standardized approach for evaluating the impact resistance of rigid plastics. By following the structured methodology, laboratories and industrial users can ensure consistent, reproducible results that meet industry and regulatory standards.
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