ISO 22088-2:2006

Overview

ISO 22088-2:2006 - "Plastics - Determination of resistance to environmental stress cracking (ESC) - Part 2: Constant tensile load method" specifies laboratory procedures to assess how thermoplastics resist environmental stress cracking (ESC) when held under a constant tensile load in the presence of chemical agents. The standard is a comparative/ranking test (not intended for design or performance prediction) and applies to specimens prepared by moulding and/or machining.

Key topics and requirements

• Test principle: Specimens are immersed or coated with a chemical agent while subjected to a constant tensile load; time and/or stress at rupture are recorded.
• Methods:
  • Method A: Determine the tensile stress that causes rupture at 100 h (interpolation of time-to-rupture vs stress).
  • Method B: Measure time to rupture under a single agreed stress (used when rupture time > 100 h).
  • Method C: Determine times to rupture for a series of stresses and evaluate results for agreed stresses (Method A is a subset of C).
• Specimens: Prefer ISO 527-2 type 1BA small specimen; preferred thickness (2 ± 0.2) mm (alternatively 3–4 mm or product thickness). Minimise residual stresses in preparation; annealing is recommended.
• Number of specimens: Minimum five specimens per stress for Methods A and B; minimum two per stress for Method C.
• Loading and measurement: Calculate force F = σA (σ = selected stress, A = cross-sectional area). Measure dimensions to 0.01 mm. Apply load smoothly (preferably 3–5 s, <10 s) and start timer at t = 0. Record time-to-rupture and fracture type.
• Apparatus and accuracy: Tensile-load device accommodating immersion or coating, inert contact materials, temperature-controlled bath or room (preferred test temps: 23 ± 2 °C and 55 ± 2 °C; other temps up to 105 ± 2 °C possible). Force accuracy ±1%; timer accuracy ±1% of elapsed time.
• Test conditions: Condition specimens ≥24 h at (23 ± 2) °C and (50 ± 10) % RH unless otherwise agreed. Ensure applied stress is less than tensile yield; as a guide, the stress giving 2% elongation after 1 h can be used as the maximum permissible stress.
• References: Normative standards include ISO 293, ISO 294-1, ISO 527-2, ISO 2818, ISO 3167 and ISO 22088-1 (general guidance).

Applications and users

ISO 22088-2 is used for:

• Comparative ranking of thermoplastic materials for resistance to environmental stress cracking
• Quality control and material screening in R&D
• Supplier/acceptance testing and formulation comparisons

Typical users:

• Polymer manufacturers and compounders
• Materials laboratories and test houses
• Automotive, packaging, consumer goods and other industries concerned with chemical exposure and surface agents

Related standards

• ISO 22088-1:2006 (general guidance)
• ISO 22088-3, -4, -5 (constant-strain and other ESC methods)
• ISO 22088-6 (slow strain rate method)

Keywords: ISO 22088-2, environmental stress cracking, ESC test, constant tensile load method, thermoplastics testing, plastics ESC resistance.