ASTM D 1822 outlines a procedure to measure the tensile-impact strength of plastics, determining the energy needed to break a specimen with a single impact. It uses standardized specimens and provides results for comparing materials, assessing processing effects, and supporting quality control.
ASTM D 1822 describes a standardized procedure for measuring the tensile-impact strength of plastics. This test method specifically determines the energy required to break standard test specimens by a single, precisely measured tensile-impact blow.
The method is designed for use with both rigid and semi-rigid plastic materials. It is especially useful for evaluating the impact characteristics of plastics that are commonly fabricated into products which may experience sudden loading or shock during service.
ASTM D 1822 recommends two principal specimen types: Type S (standard) and Type L (long), each having defined dimensions and preparing procedures. The properties measured by this standard help in comparing different materials, assessing the effects of processing variables, and ensuring consistency in quality control.
The results are typically reported in terms of the energy absorbed per unit cross-sectional area at the point of failure, which makes it possible to directly compare the tensile-impact performance of different plastics.
This standard test method is widely referenced in material specifications and by manufacturers of plastic components for applications requiring resilience against dynamic loading.
Preparation of test specimens
ASTM D 1822 requires preparation of specimens using precise dimensions and shapes, as described in the standard. Both Type S and Type L specimens are used, depending on the nature of the plastic material and the desired data. Specimens must be free of visible defects and manufactured using processes that avoid introducing stress concentrators or inconsistent thickness. Conditioning of specimens is carried out at standard laboratory conditions, typically for at least 40 hours, to ensure moisture and temperature equilibrium. The number of test samples is determined in accordance with Section 8 of the ASTM D 1822 specification.
Test setup and apparatus
The tensile-impact test is performed using a pendulum-type impact machine, as outlined by the standard.
Conducting the test
Testing involves applying a rapidly increasing tensile force to the specimen by releasing the pendulum, which pulls apart the sample at high speed. When the specimen breaks, the absorbed energy is calculated by the difference between the pendulum’s starting and ending energies. The failure should occur within the gage section of the specimen. Each valid test result is recorded for subsequent calculation.
Calculating results
The energy required to break each specimen is divided by its minimum cross-sectional area to obtain the tensile-impact strength. Results are typically reported as J/m². Maintain clear records of the following required data:
Reporting and documentation
The final report should include comprehensive data on testing conditions, material identification, test results, failure observations, and any deviations from the standard procedure. Details such as test environment, specimen preparation methods, and type of pendulum impact apparatus should be specified so that results can be replicated or compared.
Summary
ASTM D 1822 provides a reliable method for evaluating the tensile-impact strength of plastics. Following the procedure enhances comparability between materials and batches, reveals process-dependent performance, and supports quality assurance for products subject to sudden mechanical loads.
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