Overview
ISO 4433-2:1997 - Thermoplastics pipes - Resistance to liquid chemicals - Classification - Part 2: Polyolefin pipes - defines a laboratory classification system for the chemical resistance of polyolefin pipes (PE, PP, PB, PE-X) and applicable sheets. It is intended for assessing pipe material behaviour when immersed in liquids in the absence of pressure or external stress. The method is based on measured changes in mass and mechanical properties after immersion (immersion tests follow ISO 4433-1).
Key topics and technical requirements
- Purpose: Preliminary classification of chemical resistance for polyolefin pipes used for conveying liquids without pressure or mechanical stress.
- Immersion testing: Test pieces taken from pipe walls are immersed in the liquid; changes are measured at multiple times up to a reference period of 112 days (ISO 4433-1 immersion method).
- Measured parameters:
- Change in mass (Δm)
- Change in elastic modulus (Q_E)
- Change in tensile strength at yield (Q_ty)
- Change in tensile strength at break (Q_tb)
- Change in elongation at yield (Q_ey)
- Change in elongation at break (Q_eb)
- Classification symbols:
- S - satisfactory resistance
- L - limited resistance
- NS - non-satisfactory resistance
- Decision rules: Classification is determined by comparing mean percentage changes after 112 days with the limits given in the standard’s tables and by plotting results (e.g., Δm vs square root of time; lg Q vs lg time). The final classification is the most conservative (lowest) of the parameter-based results.
- Limitations and follow-up: For pressure or stressed applications, ISO 4433-2 detects incompatibilities but requires confirmation by pressure/stress testing (see ISO 8584-1). Considerations such as permeation and electrostatic charge buildup are noted.
- Test report requirements: Full identification of pipe and immersion liquid, test temperature and duration, mean percentage changes for all parameters, individual classifications and final classification, and test dates.
Practical applications and users
Who uses ISO 4433-2:1997:
- Pipe manufacturers and materials engineers assessing chemical compatibility of thermoplastics pipes (polyolefins) for chemical handling, drainage, and non-pressurized installations.
- Specifiers and procurement professionals deciding material selection for chemical service where pressure is absent.
- Test laboratories performing immersion-based chemical resistance screening.
Practical value:
- Rapid, standardized screening for chemical attack before committing to more elaborate pressure-based testing.
- Helps document suitability or incompatibility of polyolefin pipes with specific liquids and concentrations.
Related standards
- ISO 4433-1:1997 - Immersion test method (normative reference for test procedures).
- ISO 8584-1:1990 - Determination of chemical resistance factor and basic stress for polyolefin pipes under pressure (relevant for pressure applications).
- Other parts of ISO 4433 cover PVC and PVDF pipe classifications.
Keywords: ISO 4433-2:1997, polyolefin pipes, thermoplastics pipes, chemical resistance, immersion test, classification, tensile properties, change in mass.