ISO 4433-1:1997

Overview

ISO 4433-1:1997 specifies a standardized immersion test method for preliminary evaluation and classification of the chemical resistance of thermoplastics pipes (and thermoplastic sheet, where appropriate). The standard provides a laboratory procedure to determine how pipe materials respond to liquid chemicals in the absence of applied pressure or mechanical stresses, producing a preliminary classification of S (satisfactory), L (limited) or NS (not satisfactory).

Key topics and technical requirements

• Purpose: Preliminary assessment of thermoplastics pipes’ resistance to liquid chemicals by immersion and subsequent tensile testing. Not intended to assess behavior under internal pressure or high mechanical stresses.
• Test specimens: Half-size tensile test pieces (derived from ISO 527-2) cut from pipe wall (axis parallel to pipe). Preferred pipe wall thickness 1.8–3.2 mm (typically ~2.2 mm ±0.3 mm); preferred outside diameter 75–110 mm.
• Sample size: Minimum 20 test pieces per liquid and temperature; sets of at least five used for each tensile and mass-change determination.
• Immersion conditions: Standard temperatures include 23, 40, 60, 80 and 100 °C (use boiling point if lower). Immersion periods use standardized intervals (7, 14, 28, 56, 112 days). Initial tensile-test time is selected based on a plateau in the mass-change curve but shall not exceed 28 days unless equilibrium occurs later.
• Mass change measurement: Determine percentage mass change (Δm) before and after immersion; plot Δm against sqrt(time) to identify saturation/equilibrium. Formula and measurement accuracy requirements are specified.
• Tensile testing: After immersion and conditioning, tensile properties are measured (referencing ISO 527-2). Apparatus and speeds are cited; test pieces may require conditioning at 23 °C prior to testing.
• Practical test details: Minimum liquid volume per test piece (≥60 ml or 4 ml/cm²), daily stirring and weekly replacement of immersion liquid (more frequent for unstable liquids), rinsing/drying procedures depending on liquid type, and precautions for volatile or light-sensitive liquids.

Applications and users

This standard is used for:

• Manufacturers of thermoplastic pipes for chemical service seeking an initial chemical resistance classification.
• Materials and design engineers selecting pipe materials for chemical conveyance where no significant mechanical stresses are expected.
• Test laboratories performing standardized chemical-resistance screening.
• Specifiers, purchasers and regulators who require documented, comparable preliminary chemical-resistance data.

Use ISO 4433-1 results as a preliminary guide; when pressure, internal stresses or stress-cracking risks are present, perform additional tests specified in other standards before final selection.

Related standards

• ISO 175 (effects of liquid chemicals on plastics)
• ISO 527-2 (tensile properties of plastics)
• ISO 6259 series (tensile properties of thermoplastics pipes)
• ISO 8584-1 (further testing for pipes under pressure/stress)
• ISO/TR 10358 (collection of results obtained by this method)

Keywords: ISO 4433-1, thermoplastics pipes, immersion test method, chemical resistance testing, pipe classification, tensile properties, mass change, plastics pipe testing.