Overview
ISO 4433-3:1997 is part of the ISO 4433 series that defines a laboratory procedure and classification system for the chemical resistance of PVC pipes. It applies specifically to unplasticized poly(vinyl chloride) (PVC‑U), high‑impact PVC (PVC‑HI) and chlorinated PVC (PVC‑C) intended for conveying liquids in the absence of pressure or other stresses. The standard provides a preliminary classification based on immersion tests (carried out per ISO 4433‑1) and is intended to detect incompatibilities between PVC materials and liquid chemicals.
Key topics and technical requirements
- Materials covered: PVC‑U, PVC‑HI, PVC‑C (also applicable to PVC‑U sheets where appropriate).
- Test method: Immersion of pipe‑wall test pieces in the liquid chemical at specified temperatures and times (see ISO 4433‑1 for detailed procedure).
- Primary measurements:
- 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)
- Assessment time: Classification is based on measured changes after an immersion period (standard reference uses 112 days).
- Classification symbols:
- S = satisfactory resistance
- L = limited resistance
- NS = non‑satisfactory resistance
- Data analysis:
- Plot Δm versus the square root of time to evaluate mass uptake or loss.
- Plot mechanical property changes (elastic modulus, tensile strength, elongation) on log–log plots of percentage change versus immersion time.
- Limitations: The method evaluates non‑stressed conditions. For pressurized or stressed service, satisfactory or limited results must be confirmed with pressure/stress tests (see Related Standards). The standard also notes considerations such as permeation of liquids through the pipe wall and potential electrostatic charge buildup.
Applications and users
ISO 4433‑3 is used for:
- Pipe and compound manufacturers verifying material compatibility with specific chemicals during product development.
- Testing laboratories performing standardized immersion tests and producing classification reports.
- Design and specification engineers selecting PVC materials for chemical handling, drainage, and non‑pressure installations.
- Procurement and quality assurance teams requiring documented evidence of chemical resistance for materials used in industrial, laboratory or building applications.
Practical value: the standard provides an objective, reproducible preliminary classification to guide material selection and identify incompatibilities before committing to field service or more extensive pressure‑rated testing.
Related standards
- ISO 4433‑1 - Immersion test method (normative for test procedure)
- ISO 4433 (Parts 1–4) - Series covering polyolefins, PVDF, etc.
- ISO 8584‑1 and ISO/TR 8584‑2 - Methods for chemical resistance under pressure (used to confirm results for stressed or pressurized applications)
Keywords: ISO 4433-3:1997, chemical resistance of PVC pipes, PVC‑U chemical compatibility, immersion test, thermoplastics pipes classification, PVC‑HI, PVC‑C, pipe testing.