ISO 178-2019 PDF

Full title and description

ISO 178:2019 — Plastics — Determination of flexural properties. This International Standard specifies a three-point bending method to determine flexural strength, flexural modulus and the flexural stress–strain relationship of rigid and semi-rigid plastics under defined conditions, with preferred specimen dimensions and alternative sizes where appropriate.

Abstract

The standard describes a mid-span, three-point loading test on freely supported beams to investigate flexural behaviour and to determine flexural strength and modulus. It applies to thermoplastic and thermosetting moulding, extrusion and casting materials (including filled and reinforced compounds) and to rigid thermoplastic and thermosetting sheets. The method is not normally suitable for rigid cellular materials or sandwich constructions and provides parameters for specimen dimensions, conditioning and test speeds; it is intended for materials testing and quality control rather than direct design parameters.

General information

• Status: Published
• Publication date: April 2019
• Publisher: International Organization for Standardization (ISO)
• ICS / categories: 83.080.01 — Plastics in general
• Edition / version: Edition 6 (2019)
• Number of pages: 25 (ISO edition); national/adopted versions (EN, NF/BS) may show different page counts due to national forewords and annexes.

Scope

Specifies a standard test method (three-point bending) for determining flexural properties of rigid and semi-rigid plastics under specified conditions, including preferred specimen dimensions and allowable alternatives, a range of test speeds, specimen conditioning, and applicability limits (e.g., fibre-reinforced compounds with short fibres ≤ 7.5 mm; guidance to use ISO 14125 for long-fibre laminates). The method is intended for material characterization and quality control rather than direct structural design parameters.

Key topics and requirements

• Three-point bending test on a freely supported beam (midspan loading).
• Determination of flexural strength and flexural modulus and characterization of the flexural stress–strain curve.
• Preferred specimen dimensions and permitted alternative sizes (including guidance for machining specimens from multipurpose test specimens or finished products).
• Specified range of test speeds and strain-rate options (methods A and B in earlier editions; current document specifies appropriate speeds for modulus and other curve regions).
• Conditioning of specimens and recognition of factors affecting results (e.g., oriented skin layers in injection-moulded semi-crystalline polymers).
• Applicability notes and exclusions (not normally suitable for rigid cellular or sandwich materials; cross-reference to ISO 1209 series and ISO 14125 where appropriate).

Typical use and users

Used by materials testing laboratories, quality control and QA/QC departments in plastics manufacturing, research and development groups evaluating new formulations or additives, product designers seeking material property data, certification bodies and standards committees, and academic researchers studying mechanical behaviour of plastics.

Related standards

Commonly referenced and related standards include ISO 10350‑1 and ISO 10350‑2 (property presentation), ISO 14125 (flexural testing of fibre‑reinforced plastics — four‑point bending for long‑fibre laminates), ISO 1209‑1/‑2 (tests for cellular/sandwich materials), and ISO 20753 (multipurpose test specimen guidance). The standard is often published as or adopted into regional versions such as EN ISO 178:2019/NF EN ISO 178 and national adoptions (BS EN ISO 178).

Keywords

flexural properties; flexural strength; flexural modulus; three‑point bending; plastics testing; thermoplastics; thermosets; specimen dimensions; strain rate; materials characterization.

FAQ

Q: What is this standard?

A: ISO 178:2019 is an International Standard that specifies a method for determining the flexural properties of rigid and semi‑rigid plastics using a three‑point bending test.

Q: What does it cover?

A: It covers test specimen dimensions, conditioning, test speeds/strain rates, and procedures to measure flexural strength, flexural modulus and the flexural stress–strain relationship for a wide range of thermoplastic and thermosetting materials, with notes on applicability and exclusions (e.g., cellular/sandwich structures and long‑fibre laminates).

Q: Who typically uses it?

A: Materials test laboratories, QC/QA teams in plastics manufacturing, R&D engineers, standards bodies, certification bodies and researchers working with plastic materials and components.

Q: Is it current or superseded?

A: ISO 178:2019 is the current published edition (published April 2019). The ISO registry indicates the standard is in the review cycle and may be subject to revision in accordance with ISO review procedures; previous editions include ISO 178:2010 and earlier. National/adopted versions (EN, NF, BS) reflect the 2019 edition as EN ISO 178:2019.

Q: Is it part of a series?

A: It is part of the suite of ISO standards for plastics testing maintained by ISO/TC 61 (Plastics) and is cross‑referenced with other plastics test methods (e.g., ISO 10350, ISO 14125, ISO 1209 series, ISO 20753). Regional/adopted versions (EN ISO, NF EN ISO, BS EN ISO) exist for use within specific markets.

Q: What are the key keywords?

A: Flexural properties, flexural strength, flexural modulus, bending test, three‑point loading, plastics testing, specimen dimensions, strain rate.