ISO 182-2:1990

Overview

ISO 182-2:1990 - Plastics: Determination of the tendency of PVC compounds and products to evolve hydrogen chloride (HCl) and other acidic products at elevated temperatures - Part 2: pH method.

This ISO procedure defines a pH-based laboratory test to assess the thermal stability of materials based on vinyl chloride homopolymers and copolymers (PVC). The method measures the evolution of hydrogen chloride during controlled heating by absorbing evolved HCl into a 0.1 mol·L‑1 sodium chloride solution and recording the pH change. The measured stability time is the time to reach a specified pH endpoint (test uses pH 3.8).

Key topics and technical requirements

• Test principle: Heat a known mass of PVC in a dehydrochlorination cell under an inert gas stream; absorb evolved HCl in 0.1 mol·L‑1 NaCl and monitor pH drop.
• Sample size & preparation: Typical test portion is 2 g, prepared according to material form (plastisols, pellets, films, coatings, cables); avoid excessive heating during grinding; not recommended for dry blends.
• Apparatus & reagents:
  • Dehydrochlorination cell (re-usable Cell A or disposable Cell B)
  • Pure nitrogen supply (O2 < 6 ppm; CO2 < 0.1 ppm)
  • Flow rate ~120 cm3/min ± 4 cm3/min
  • Oil bath capable of 170–210 °C with ±0.1 °C control
  • Measurement cell with 180 mL NaCl solution, magnetic stirrer, pH‑meter (accuracy 0.01 pH)
  • Sodium chloride solution c(NaCl) = 0.1 mol·L‑1; pH adjusted to ~6.0 prior to test
• Temperatures: Recommended test temperatures-200 °C for unplasticized and cable compounds; 180 °C for plasticized materials.
• Endpoint & result: Record the time (minutes) for pH to fall to 3.8 - reported as the stability time tS (nearest 0.5 minute, include replicate values and mean).
• Limitations: Other acidic decomposition products may affect pH; if non‑HCl acids are significant, use an ion‑specific method (see ISO 182‑4).

Applications and users

• Quality control during manufacture and conversion of PVC compounds and coloured products.
• Comparative evaluation of heat‑stabiliser effectiveness and formulation stability.
• Suitable for manufacturers of PVC compounds, compounders, converters, R&D laboratories, materials testing labs, and compliance/quality engineers concerned with thermal ageing and dehydrochlorination performance.

Related standards

• ISO 182 (other parts): Part 1 (Congo red method), Part 3 (Conductometric method), Part 4 (Potentiometric / chloride‑specific method).
• Normative references cited: ISO 3696 (water quality), ISO 4793 (sintered filters), ISO 565 (sieves), ISO 6353‑2 (reagents).

Keywords: ISO 182-2:1990, PVC thermal stability, hydrogen chloride evolution, dehydrochlorination test, pH method, plastics testing, quality control for PVC.