ISO 4433-4:1997

Overview

ISO 4433-4:1997 - Thermoplastics pipes - Resistance to liquid chemicals - Part 4: Poly(vinylidene fluoride) (PVDF) pipes - provides a standardized method for preliminary classification of the chemical resistance of PVDF pipes and sheets. The standard is based on immersion testing (referencing ISO 4433-1) and assesses how PVDF pipe material properties change after exposure to liquids in the absence of pressure or mechanical stress.

Key topics and requirements

• Scope: Classification of chemical resistance for PVDF pipes used without internal pressure or external stress; useful as a preliminary screening method.
• Test method: Immersion tests using specimens cut from pipe walls, performed in accordance with ISO 4433-1 (immersion test method).
• Measured parameters:
  • Change in mass (Δm)
  • Change in elastic modulus (Q_E)
  • Change in tensile strength at break (Q_tb)
  • Change in elongation at break (Q_eb)
• Test duration: Classification uses the arithmetic mean results after 112 days' immersion (plots over time are also used).
• Classification symbols:
  • S - satisfactory resistance
  • L - limited resistance
  • NS - non-satisfactory resistance
    Final classification is the more conservative (lower) result derived from the measured parameters.
• Reporting requirements: Test reports must reference ISO 4433-4 and include complete pipe identification, immersion liquid details (type, concentration), temperature, immersion period, mean percentage changes for the measured parameters, classifications for each parameter and the final classification, and test dates.

Practical applications

• Provides manufacturers, material engineers, specifiers and end-users with a reproducible basis to screen PVDF materials for compatibility with specific liquids when pipes are used under non-pressurized conditions.
• Useful during material selection, quality control and specification writing for corrosion-resistant piping systems, chemical handling lines, and industrial piping where PVDF is considered for its chemical resistance and halogenated-polymer properties.
• Acts as a preliminary step: where pipes will operate under pressure or stress, ISO 4433-4 results indicate incompatibilities but must be followed by pressurized tests (see Related Standards).

Related standards

• ISO 4433-1:1997 - Immersion test method (normative reference used by this part).
• ISO 8584-1 and ISO/TR 8584-2 - referenced for additional testing and confirmation when pipes are to be used under pressure or stress.

Keywords: ISO 4433-4, PVDF pipes, chemical resistance, thermoplastics pipes, immersion test, classification, PVDF chemical compatibility.