ISO 18488:2025 PDF

Polyethylene (PE) materials for piping systems — Determination of strain hardening modulus in relation to slow crack growth — Test method

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Title (English):

ISO 18488:2025

Polyethylene (PE) materials for piping systems — Determination of strain hardening modulus in relation to slow crack growth — Test method

Document status:: Active
Format:: Electronic (PDF)
Number of pages:: 10
Publication date:: October 14, 2025
Edition:: ISO IS 18488 edition 2 version 1
ICS:: 23.040.20

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Description (English):

This document specifies a method for the determination of the strain hardening modulus, which is used as a measure for the resistance to slow crack growth of polyethylene. This document specifies how to obtain a strain hardening modulus measurement from “true stress vs. draw ratio” curves on compression moulded samples. Details of the necessary equipment, precision and sample preparation for the generation of data are given. This document provides a method that is valid for all types of polyethylene, independent from the manufacturing technology, comonomer or catalyst type used for pipes and fittings applications.

Technical details

Technical committee: ISO/TC 138/SC 5 - General properties of pipes, fittings and valves of plastic materials and their accessories -- Test methods and basic specifications
SKU: ISO 18488:2025

Abstract

Overview

ISO 18488:2025 specifies a laboratory test method for determining the strain hardening modulus of polyethylene (PE) materials used in piping systems. The strain hardening modulus, obtained from true stress vs. draw ratio curves on compression‑moulded sheets, is used as an intrinsic measure of a material’s resistance to slow crack growth (SCG). This second edition updates definitions, specimen handling and data‑analysis guidance and applies to all PE types regardless of manufacturing route, comonomer or catalyst.

Key topics and technical requirements

Test principle: tensile testing of compression‑moulded specimens at 80 ± 1 °C, recording true stress vs. draw ratio beyond the natural draw ratio to extract the strain hardening modulus.
Specimen preparation: compression moulding per ISO 293 into sheets of 0.30 mm or 1.0 mm thickness, annealing and punching five specimens free of defects.
Specimen geometry: defined gauge length, narrow parallel section (4.0 mm width) and specified radii and overall lengths to avoid grip failure.
Test equipment:
- Tensile machine and speed 20 ± 2 mm/min (conforming to ISO 527‑1).
- Load cell Class 1 (ISO 7500‑1) and extensometer Class 1 (ISO 9513) capable up to draw ratio λ = 12.
- Temperature chamber to maintain 80 °C and suitable grips to prevent slippage or premature fracture.
Measurements and tolerances: thickness measured to 0.005 mm accuracy, width to 0.01 mm; gauge marks and alignment requirements; use of the lowest measured thickness and average width in data analysis.
Data analysis: slope of a Neo‑Hookean constitutive model fitted to data between draw ratio 8 and up to maximum stress (but not above λ = 12) defines the strain hardening modulus .

Applications and who should use it

Material suppliers evaluating PE grades for resistance to environmental stress cracking and long‑term SCG performance.
Pipe and fitting manufacturers for quality control, product development and material selection decisions.
Testing laboratories performing polymer characterization and comparative assessments of PE formulations.
R&D teams correlating microstructure, processing and lifetime performance of PE piping materials.

Practical benefits include a fast, reproducible measurement (independent of long SCG test durations) that correlates with established ESCR/PNET/FNCT/CRB performance indicators.

Related standards

ISO 293 - Compression moulding of thermoplastic test specimens
ISO 527‑1 - Tensile properties - General principles
ISO 7500‑1 - Calibration of force‑measuring systems
ISO 9513 - Calibration of extensometer systems

Keywords: ISO 18488:2025, strain hardening modulus, polyethylene (PE), slow crack growth, PE piping, true stress vs. draw ratio, compression moulded specimens, tensile test, ESCR.

Related standards

Standards mentioned in the description

Abstract

Overview

Key topics and technical requirements

Test principle: tensile testing of compression‑moulded specimens at 80 ± 1 °C, recording true stress vs. draw ratio beyond the natural draw ratio to extract the strain hardening modulus.
Specimen preparation: compression moulding per ISO 293 into sheets of 0.30 mm or 1.0 mm thickness, annealing and punching five specimens free of defects.
Specimen geometry: defined gauge length, narrow parallel section (4.0 mm width) and specified radii and overall lengths to avoid grip failure.
Test equipment:
- Tensile machine and speed 20 ± 2 mm/min (conforming to ISO 527‑1).
- Load cell Class 1 (ISO 7500‑1) and extensometer Class 1 (ISO 9513) capable up to draw ratio λ = 12.
- Temperature chamber to maintain 80 °C and suitable grips to prevent slippage or premature fracture.
Measurements and tolerances: thickness measured to 0.005 mm accuracy, width to 0.01 mm; gauge marks and alignment requirements; use of the lowest measured thickness and average width in data analysis.
Data analysis: slope of a Neo‑Hookean constitutive model fitted to data between draw ratio 8 and up to maximum stress (but not above λ = 12) defines the strain hardening modulus .

Applications and who should use it

Material suppliers evaluating PE grades for resistance to environmental stress cracking and long‑term SCG performance.
Pipe and fitting manufacturers for quality control, product development and material selection decisions.
Testing laboratories performing polymer characterization and comparative assessments of PE formulations.
R&D teams correlating microstructure, processing and lifetime performance of PE piping materials.

Practical benefits include a fast, reproducible measurement (independent of long SCG test durations) that correlates with established ESCR/PNET/FNCT/CRB performance indicators.

Related standards

ISO 293 - Compression moulding of thermoplastic test specimens
ISO 527‑1 - Tensile properties - General principles
ISO 7500‑1 - Calibration of force‑measuring systems
ISO 9513 - Calibration of extensometer systems

Keywords: ISO 18488:2025, strain hardening modulus, polyethylene (PE), slow crack growth, PE piping, true stress vs. draw ratio, compression moulded specimens, tensile test, ESCR.

ISO 18488:2025 PDF

Technical details

Abstract

Overview

Key topics and technical requirements

Applications and who should use it

Related standards

Related standards

Abstract

Overview

Key topics and technical requirements

Applications and who should use it

Related standards

Related standards

Plastics - Compression moulding of test specimens of thermoplastic materials (ISO 293:2023)

Plastics - Determination of tensile properties - Part 1: General principles (ISO 527-1:2019)

Metallic materials — Verification of static uniaxial testing machines — Part 1: Tension/compression testing m…

Metallic materials - Calibration of extensometer systems used in uniaxial testing - Technical Corrigendum 1 (…