Information on the most widely used ASTM standards within the materials testing industry
ISO 16241: Notch tensile test to measure the resistance to slow crack growth of polyethylene materials for pipe and fitting products.
Standard scope:
It is the global benchmark accelerated test for evaluating slow crack growth (SCG) resistance of polyethylene (PE) pipe and fitting materials, directly derived from ASTM F1473.
Test Method Overview:
Core Purpose: Quantify the resistance of polyethylene to slow, brittle crack propagation under constant tensile load, elevated temperature, and a sharp notch.
Accelerated Conditions (Standard):
Temperature: 80 °C
Applied Stress: 2.4 MPa
Failure Mode: Brittle fracture via slow crack growth from the notch tip (no ductile yielding).
Output: Time-to-failure (hours/days) under specified conditions; longer time = better SCG resistance.
Test Principle of ISO 16241:
The core principle of this test is: for square cross-section specimens with mechanical notches in four directions, under the combined effects of constant tensile stress (2.4Mpa), high temperature (usually 80°C), and a surfactant environment, the slow crack growth process initiated from the notches in the material is accelerated. By measuring the time required for the specimen to fracture, the material's resistance to environmental stress cracking and slow crack growth can be quantitatively evaluated. The longer the time, the better the performance.
Test Equipment Required:
| Equipment | Key Requirements |
|---|---|
| Constant-Load Tensile Frame | Lever‑type (5:1 ratio preferred), dead‑weight, or computer controlled servo‑controlled; maintains constant tensile load. |
| Temperature‑Controlled Chamber | Maintains 80 ± 1 °C; uniform air circulation |
| Notching Machine | Razor‑blade notcher to create a sharp, controlled V‑notch (main depth ~3.5 mm; side groove: 1mm)
|
| Alignment Jig | Ensures specimen/grip alignment to avoid bending stress.
|
| Timer | Accuracy ≥ 1%; auto‑stops on specimen failure |
| Specimen Grips | Smooth, non‑slip; no notch damage during clamping |
Applications and Importance of the ISO 16241 PENT Notch tensile test for resistance of slow crack growth:
Main Applications: Specifically used to evaluate the long-term resistance to slow crack growth of high-grade polyethylene pipe resins (such as PE 100 and PE 100-RC). It is a key test for material grading and quality control in the pipeline industry.
Importance: PENT notch test simulates the complex stress state that pipelines experience under internal pressure during actual service through a multiaxial stress state (generated by four notches), which reflects real conditions better than uniaxial tensile tests. Its results are highly correlated with the long-term (over 50 years) hydrostatic strength and stress crack resistance of pipelines. Materials screened through this test provide the fundamental guarantee for the long-term safe operation of pressure pipeline systems such as gas and water supply.
Related Standards
| ASTM F1473 | The original PENT test (ISO 16241 is based on this standard). Standard Test Method for Notch Tensile Test to Measure the Resistance to Slow Crack Growth of Polyethylene Pipes and Resins. |
| EN 12201 | Plastics piping systems for water supply, and for drainage and sewerage under pressure - Polyethylene (PE). (mainly the hydrostatic pressure test, Melt flow index test, tensile and elongation test, Oxygen induction time test.) |
| ISO 9080 | Plastics piping systems — Long‑term hydrostatic pressure testing (real‑time SCG correlation) |
| ISO 13479 | Polyolefin pipes — Determination of resistance to crack propagation — Notched pipe test (full‑pipe SCG validation) |
| ASTM F2136 | Standard Test Method for Notched, Constant Ligament-Stress (NCLS) Test to Determine Slow-Crack-Growth Resistance of HDPE Resins or HDPE Corrugated Pipe |
Related products and device
Related Standard
ASTM F1473 test method determines the resistance of polyethylene materials to slow crack growth under conditions specified within.
ASTM F1473 standard test is performed at 80 °C and at 2.4 MPa, but it shall be acceptable to conduct tests at a temperature below 80 °C and with other stresses low enough to preclude ductile failure and thereby eventually induce brittle type of failure. The standard test is conducted in an air environment; however, it shall be acceptable to immerse test specimens in an alternate environment such as water or a water/detergent solution, or other liquid or a different environment such as an inert gas to evaluate slow crack growth performance in different environments. Generally, polyethylenes will ultimately fail in a brittle manner by slow crack growth at 80 °C if the stress is at or below 2.4 MPa
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