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ASTM D 256:1997

Standard Test Methods for Determining the Izod Pendulum Impact Resistance of Plastics

German title
Prüfschlagfestigkeit von Kunst- und Isolierstoffen
Publication date
1997
Original language
English
Publication date
1997
Original language
English

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Short description
1. Scope 1.1 These test methods cover the determination of the resistance of plastics to breakage by flexural shock as indicated by the energy extracted from "standardized" (see Note 1) pendulum-type hammers, mounted in "standardized" machines, in breaking standard specimens with one pendulum swing. The standard tests for these test methods require specimens made with a milled notch (see Note 2). In the Charpy (Test Method B) and Izod (Test Methods A, C, and D) tests, the notch produces a stress concentration which promotes a brittle, rather than a ductile, fracture. In Test Method E, the impact strength is obtained by reversing the position in the vise of a notched specimen. The results of all tests are reported in terms of energy absorbed per unit of specimen width (see Note 3). Note 1-The machines with their pendulum-type hammers have been "standardized" in that they must comply with certain requirements, including a fixed height of hammer fall which results in a substantially fixed velocity of the hammer at the moment of impact. However, besides the fact that the designs of machines for use with Test Methods A and B (see Section 4) must be somewhat different, hammers of different initial energies (produced by varying their effective weights) are recommended for use with specimens of different impact strengths. Moreover, manufacturers of the equipment are permitted to use different lengths and constructions of pendulums with resulting possible differences in pendulum rigidities (see Section 5), plus other differences in machine design. The specimens are "standardized" in that they are required to have either one of two fixed lengths (Test Methods A and B), one fixed depth and one particular design of milled notch. The width of the specimens is permitted to vary between limits. Note 2-The notch in the Izod specimen serves to concentrate the stress, minimize plastic deformation, and direct the fracture to the part of the specimen behind the notch. Scatter in energy-to-break is thus reduced. However, because of differences in the elastic and visco-elastic properties of plastics, response to a given notch varies among materials. A measure of a plastics "notch sensitivity" may be obtained with Test Method D by comparing the energies to break specimens with identical notches, except for the radius at the base of the notch. Note 3-Caution must be exercised in interpreting the results of these standard test methods. The following testing parameters may affect test results significantly: method of fabrication, including but not limited to processing technology, molding conditions, mold design, and thermal treatments; method of notching; speed of notching tool; design of notching apparatus; quality of the notch; time between notching and test; test specimen thickness, and environmental conditioning 1.2 The values stated in SI units are to be regarded as the standard. The values stated in parentheses are for information only. 1.3 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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