Overview
ISO 3451-5:2025 - Plastics - Determination of ash - Part 5: Poly(vinyl chloride) defines standardized laboratory procedures to measure the ash content of poly(vinyl chloride) (PVC) materials. The third edition updates test conditions for common fillers, adds thermobalance as an alternative technique for Method A, and clarifies reproducibility for sulfated-ash procedures when lead-containing compounds are present. The document applies to PVC resins, compounds and finished products.
Key topics and requirements
- Three analytical methods
- Method A (direct calcination): Burn off organic matter and heat residue to a specified temperature until constant mass is reached. Can use muffle, microwave furnace or thermobalance.
- Method B (sulfated ash after combustion): Calcination, then treatment of residue with concentrated sulfuric acid, followed by reheating at 950 °C.
- Method C (sulfated ash before combustion): Add concentrated sulfuric acid before combustion and then calcinate at 950 °C. Recommended over B for better reproducibility.
- Applicability
- All three methods: resins, compounds, finished products.
- Methods B and C: specifically applicable when lead-containing compounds are present (not recommended with thermobalance).
- Calcination temperatures (examples given)
- Unfilled PVC and many fillers: 950 °C ± 50 °C
- PVC with calcium carbonate (CaCO3): 1 100 °C ± 50 °C
- Glass fibres / bubbles: 600 °C ± 25 °C
- Thermobalance temperature tolerance: ±5 °C
- Equipment & precision
- Crucibles of Al2O3, silica, platinum or porcelain; muffle/microwave furnace or thermobalance; analytical balance ±0.1 mg.
- Test portion masses defined (e.g., resin 5 g; filled products 2 g or 5 g).
- Constant-mass criterion: two consecutive weighings differing by ≤ 0.5 mg; maximum routine furnace time guidance provided.
- Safety
- Hazard warnings: thermal decomposition of PVC releases hydrogen chloride; concentrated sulfuric and acetic acids used for sulfation. Use fume hood, PPE and proper acid-handling practice.
Applications and users
- Quality control laboratories in PVC resin and compound production
- Raw-material suppliers and pigment/filler manufacturers (e.g., CaCO3, talc, glass fillers)
- Regulatory and compliance testing for material composition and filler content
- R&D and failure analysis teams assessing inorganic residue, filler distribution or contamination
- Accredited testing labs preparing reports for product specifications and standards compliance
Related standards
- ISO 3451-1 - Plastics - Determination of ash - Part 1: General methods (general procedures referenced)
- ISO 11358-1 - Plastics - Thermogravimetry (TG) of polymers - Part 1: General principles (thermobalance guidance)
Keywords: ISO 3451-5:2025, PVC ash determination, sulfated ash, calcination, thermobalance, muffle furnace, plastics testing, lead-containing compounds.
