ISO 8361-3:1991

Overview

ISO 8361-3:1991 specifies test conditions for determining water absorption of acrylonitrile/butadiene/styrene (ABS) pipes and fittings. As Part 3 of the ISO 8361 series, it complements the general method in ISO 8361‑1 by defining the exact conditioning, immersion and measurement steps for ABS materials used in thermoplastics pipes and fittings. The part also supplies an informative preferred maximum value for water absorption to support product specification and quality control.

Key topics and requirements

• Scope and materials: Applies to ABS pipes and fittings that contain only the necessary antioxidants, stabilizers and pigments; materials should meet ISO 7245 requirements.
• Test principle: Condition test pieces, measure mass and total surface area, immerse in hot distilled water, re‑measure mass and calculate change in mass per unit area (water absorption).
• Conditioning and pre‑test handling:
  • Condition in a forced‑air oven at 90 °C ± 2 °C for 2 h.
  • Cool in air at 23 °C ± 2 °C, 50 % ± 5 % RH for 15 min ± 1 min before initial mass/area measurement.
• Immersion:
  • Immerse in distilled water at (90 ± 1) °C for 24 h.
  • After immersion, cool in bath at 23 °C ± 2 °C for 15 min ± 1 min, wipe with filter paper and determine final mass.
• Result expression: Report water absorption as change in mass per unit area according to the procedures and calculation clauses in ISO 8361‑1.
• Preferred maximum: Annex A (informative) indicates a preferred maximum water absorption value (informative guidance for specifications).

Practical applications and users

Who uses ISO 8361-3:1991:

• Manufacturers of ABS pipes and fittings for plumbing, drainage and fluid transport who need material acceptance criteria.
• Quality control and testing laboratories performing water absorption tests for product verification and batch release.
• Standards committees and product designers referencing standard test conditions when writing product standards or specifications.
• Procurement, compliance and regulatory bodies requiring demonstrated resistance to water uptake for long‑term performance.

Why it matters:

• Water absorption affects mechanical properties, dimensional stability and service life of thermoplastic piping. Standardized test conditions ensure consistent, comparable results across labs and suppliers and support material selection and compliance.

Related standards

• ISO 8361‑1:1991 - Thermoplastics pipes and fittings - Water absorption - Part 1: General test method (test principle and calculation methods referenced throughout).
• ISO 7245:1984 - Requirements for pipes and fittings materials (material suitability).
• ISO 3126:1974 - Plastics pipes - Measurement of dimensions (dimensional measurement methods).

Keywords: ISO 8361-3:1991, ABS pipes, water absorption test, thermoplastics pipes and fittings, test conditions, ISO 8361, quality control, distilled water immersion.