ISO 16770:2019

Overview

ISO 16770:2019 specifies the Full-Notch Creep Test (FNCT) for assessing environmental stress cracking (ESC) resistance of polyethylene (PE) materials. The method subjects notched PE specimens-machined from moulded sheets or finished products-to a static tensile load while immersed in a controlled test environment (commonly a surfactant/detergent solution) at a specified temperature. The primary output is the time to failure, which characterizes ESC behavior for material selection, quality control and product development.

Key topics and requirements

• Scope and purpose
  • Designed specifically for polyethylene (PE) and PE products (pipes, fusion welds/fittings, blow‑moulded containers).
  • Applicable to test specimens moulded or machined from finished parts; processing-induced stresses/orientation can influence results.
• Test principle
  • Square-section bar with coplanar full notches; plane-strain geometry to promote brittle failure under a static tensile load in a controlled medium.
• Specimen types and preparation
  • Multiple specimen geometries are covered (e.g., Type A - 10 mm × 10 mm, Type B - 6 mm × 6 mm) and include injection-moulded or compression-moulded preparation and notching procedures.
• Test environment
  • Surfactant/detergent solutions are typical; distilled water or specific chemical media may be used for application-relevant testing. Extended (accelerated) conditions are defined for high crack-resistant PEs (e.g., PE 100 RC).
• Measurement and calculations
  • Record time to brittle failure; measure the post-failure ligament area to determine actual tensile stress (σL).
  • Interpolate test data to a reference tensile stress (σL,ref) to report comparable time-to-failure (tf,ref).
• Apparatus and verification
  • Loading devices must meet verification requirements (refer ISO 7500-2). Lever-arm machines are a common example.
• Precision and reporting
  • The standard includes precision/ repeatability statements from interlaboratory studies and prescribes the test report content.

Applications and users

• Useful for: materials engineers, product designers, QA/QC laboratories, polymer testing labs, pipe and container manufacturers, and regulatory bodies.
• Practical uses:
  • Material selection and comparative ranking of PE grades for ESC resistance.
  • Production monitoring and acceptance testing of pipes, fittings, welds and mouldings.
  • Evaluating effects of chemical exposures, transport of dangerous goods, or aggressive environments on PE products.
  • Accelerated screening of new crack‑resistant PE formulations.

Related standards

• ISO 294-1 (injection moulding of test specimens)
• ISO 2818 (preparation of test specimens by machining)
• ISO 7500-2 (verification of tension/creep testing machines)
• ISO 17855-2 (PE moulding/extrusion materials - specimen prep)
• ISO 20753 (test specimens)

Keywords: ISO 16770, FNCT, environmental stress cracking, ESC, polyethylene, PE, full-notch creep test, time to failure, ligament area, PE 100 RC.