ASTM D256-24 PDF

Full title and description

ASTM D256-24 — Standard Test Methods for Determining the Izod Pendulum Impact Resistance of Plastics. This standard specifies standardized pendulum (Izod) impact test methods, specimen geometry and notching procedures, machine requirements, conditioning, calculation and reporting conventions used to measure the energy absorbed by plastic specimens struck by a pendulum hammer.

Abstract

This document describes procedures to determine the Izod pendulum impact resistance of plastics using standardized specimens with a milled notch. It defines multiple test methods (including cantilever-beam and low-energy variants), specimen preparation and conditioning, machine calibration and corrections (for example toss and bending losses), failure classification, units of report, and limitations of the method. The standard is intended for quality control, specification and comparative evaluation of plastics’ notch-sensitive impact behavior.

General information

• Status: Active (current revision D256-24).
• Publication date: 2024 (D256-24); documented last updated January 1, 2025.
• Publisher: ASTM International.
• ICS / categories: Plastics testing — ICS 29.035.20 (plastics and rubber insulating materials); ASTM Committee D20 (Plastics).
• Edition / version: ASTM D256‑24 (current revision).
• Number of pages: 20 pages.

Scope

These test methods cover determination of the resistance of plastics to pendulum-type hammers using standardized specimens and machines. Methods include cantilever-beam (Izod) tests for a range of energies, a low-energy procedure for materials with low impact resistance, and related options for notch geometry and specimen dimensions. The standard gives requirements for machine design and calibration, specimen notching, conditioning, test execution, calculation of absorbed energy per unit width or cross-sectional area, and classification of failure types. It does not address all safety considerations; users must adopt appropriate safety and environmental practices.

Key topics and requirements

• Definition of test methods (Test Method A — cantilever-beam Izod; Test Method C — low-energy cantilever; plus additional test method options and notching variants).
• Standard specimen dimensions, notch geometry and notching procedures to ensure reproducibility.
• Machine requirements, pendulum energy classes, calibration and verification procedures.
• Energy accounting and corrections: fracture initiation and propagation, toss (throw) correction, bending and vibrational losses, friction and indentation losses.
• Specimen conditioning and environmental controls (temperature, humidity) and reporting of conditioning details.
• Failure classification codes (Complete Break, Hinge Break, Partial Break, Non‑Break) and rules for reporting averages by failure category.
• Units and reporting conventions (SI units are primary; customary units permitted in parentheses), and limitations when comparing data from different machines or test conditions.
• Notes on limitations and comparability with other instruments (digital vs manual testers) and differences relative to ISO/other standards.

Typical use and users

Used by polymer and compound manufacturers, materials and quality control laboratories, product designers and R&D groups to assess notch sensitivity and impact toughness of thermoplastics and some thermosets. Typical applications include incoming material qualification, process control, specification compliance, comparative ranking of formulations, and failure analysis where notch-type impact resistance is relevant.

Related standards

Standards commonly referenced with ASTM D256 include ISO 180 (Izod impact test — similar title but different contents/requirements), ASTM D6110 (Charpy pendulum impact test for plastics), ISO 179 (Charpy impact), and other ASTM and ISO standards covering specimen preparation, conditioning, and mechanical test methods for plastics. Material- or product-specific specifications may supersede some test parameters in D256.

Keywords

Izod, impact resistance, pendulum impact, plastics, notch toughness, notch sensitivity, toss correction, fracture initiation, fracture propagation, specimen notching, impact test, ASTM D256

FAQ

Q: What is this standard?

A: ASTM D256-24 is the current ASTM standard that specifies standardized Izod pendulum impact test methods for measuring the impact resistance of plastic materials using notched specimens.

Q: What does it cover?

A: It covers specimen geometry and notching, machine and pendulum requirements, conditioning, test execution, energy calculations and corrections (including toss and bending losses), failure-type classification, units and reporting conventions, and limitations for comparison between results.

Q: Who typically uses it?

A: Polymer manufacturers, materials testing laboratories, product development and quality engineers, and standards/specification authors who need a repeatable method to quantify and compare notch-sensitive impact resistance of plastics.

Q: Is it current or superseded?

A: The D256-24 revision is the current active version (ASTM D256‑24). The document record indicates an updated/active status as of January 1, 2025; users should confirm they have the D256‑24 text when testing.

Q: Is it part of a series?

A: D256 is a long-established ASTM test method and is often used alongside other impact and mechanical test standards (for example Charpy impact methods and related ISO impact standards) and product-specific ASTM test series; it is maintained under ASTM Committee D20 (Plastics).

Q: What are the key keywords?

A: Izod, impact strength, pendulum, notch, notch sensitivity, plastics testing, impact resistance, fracture propagation, toss correction.