Overview
ISO 23948:2023 - Plastics - Intumescence properties of PVC materials and products - Test method for the measurement of expansion with the cone calorimeter - specifies a laboratory test method to quantify the intumescence (expansion) of PVC materials and PVC blends when exposed to radiative heat. Using a cone calorimeter heater, specimens are exposed horizontally under ambient air to a predetermined heat flux (notably 50 kW/m² in the method) and the increase in thickness is measured before and after the test to calculate an expansion rate that characterizes intumescence.
Key topics and technical requirements
- Test principle: Measure thickness increase of PVC specimens exposed to a conical radiant electrical heater; expansion rate expressed as percentage increase of thickness.
- Specimens & conditioning: Guidance on specimen selection, dimensions and conditioning in line with standard atmospheres (ISO 554).
- Heat flux & exposure: Tests use a controlled incident radiative heat flux (method example uses 50 kW/m²); cone heater must provide uniform flux (central 50 × 50 mm area within ±2 % at 50 kW/m²) and up to at least 70 kW/m² capability.
- Equipment: Cone-shaped radiant electrical heater, heat flux meter, thermocouples, specimen holder/carousel, fume hood/extraction and dimensional measuring devices. Heater control requires stable thermocouple temperature (controller tolerance noted in the standard).
- Calibration and measurement: Calibration procedures for heat flux meters and conical heater; measurement of initial and final specimen thickness; calculation of expansion rate (percentage thickness increase).
- Scope: Applicable to PVC and blends (e.g., PVC-SAN), and intended to characterize intumescence relevant to reaction-to-fire and fire-resistance performance.
Applications and who uses it
- Fire testing laboratories conducting repeatable intumescence measurements for product evaluation.
- PVC compounders and manufacturers using the method for formulation development, quality control and comparison of intumescent additives.
- Product designers and safety engineers assessing how PVC components (window casings, gasketing, firestopping materials) will behave under radiative heat exposure.
- Regulatory bodies and specifiers that require standardized data on intumescence for compliance, classification, or performance-based fire engineering.
Practical uses include material selection, flame-retardant evaluation, and validating passive fire protection properties where intumescence reduces heat transfer and flammable gas release.
Related standards
Key referenced and related documents include ISO 5660-1, ISO 13927, ISO 17554 (cone heater and mass loss methods), ISO 554 (conditioning), ISO 1043 (polymer symbols), ISO 13943 (fire safety vocabulary), and ISO/TR 20118 for broader PVC fire properties.
Keywords: ISO 23948:2023, PVC intumescence, cone calorimeter, expansion rate, heat flux, fire testing, reaction-to-fire, PVC blends.