ISO 182-3:2025

Overview

ISO 182-3:2025 - Plastics: Determination of the tendency of PVC compounds and products to evolve hydrogen chloride at elevated temperatures - Part 3: Conductometric method.
This ISO method specifies a conductometric test to evaluate the thermal stability of vinyl chloride homopolymers and copolymers (PVC) that undergo dehydrochlorination (HCl evolution). It is intended for characterization of compounded PVC materials and products, and for assessing the effectiveness of heat‑stabilizing systems where discoloration tests are unsuitable.

Key topics and requirements

• Test principle: A sample is heated in a nitrogen stream; evolved HCl is absorbed in demineralized water and quantified by the change in the water’s conductivity. The measured parameter is the stability time (ts) - the time for a defined conductivity change.
• Reagents and gas purity: Use analytical‑grade reagents. Nitrogen purity: < 6 ppm O2 and < 0.1 ppm CO2; gas flow validation includes passing N2 through demineralized water at (7.2 ± 0.1) L/h with no conductivity change.
• Absorbing medium: Demineralized water with conductivity ≤ 5 µS/cm.
• Apparatus: Dehydrochlorination cells (Cell A reusable, Cell B disposable), measurement cell, conductance meter/electrodes, heated bath or block (capable of 170–210 °C, maintained to ±0.1 °C), flowmeter and drying agent for N2.
• Sample handling: Clauses detail preparation for plastisols, pellets, films, coatings, cable insulation, etc.; dry blends are excluded because of likely inhomogeneity.
• Limitations: Not applicable to materials that evolve other decomposition products that alter water conductivity-ISO 182-4 is recommended in that case for chloride ion determination.
• Accuracy and comparability: The document includes precision data (repeatability and reproducibility) and a comparison with the pH‑meter method in ISO 182-2.

Applications and users

• Quality control and R&D of PVC formulations to verify heat‑stabilizer performance.
• Materials selection for coloured PVC products where visual discoloration tests are unreliable.
• Cable and wire manufacturers, extrusion and moulding labs assessing thermal ageing and HCl release.
• Independent testing laboratories performing standardized assessments for compliance, material specifications, and supplier verification.
• Regulatory and safety evaluations where quantifying HCl evolution is necessary for end‑use risk assessment.

Related standards

• ISO 182-2: pH‑meter method (comparison referenced)
• ISO 182-4: Determination of chloride ion in absorbing solutions (when other decomposition products interfere)
• Normative references used in ISO 182-3: ISO 565, ISO 4793, ISO 6353-2

Keywords: ISO 182-3:2025, conductometric method, PVC thermal stability, dehydrochlorination, hydrogen chloride evolution, heat‑stabilizers, conductometry, PVC testing.