Overview
ISO 9773:1998 - Plastics - Determination of burning behaviour of thin flexible vertical specimens in contact with a small‑flame ignition source - is a small‑scale laboratory screening method for comparing the burning behaviour of thin, flexible plastic specimens exposed to a low‑energy flame. The standard defines specimen geometry, conditioning, apparatus, test procedure and result reporting to measure afterflame and afterglow times for vertically oriented thin plastics that cannot be evaluated by ISO 1210 Method B.
Key topics and technical requirements
- Specimen geometry and preparation
- Standard size: 200 mm ± 5 mm long, 50 mm ± 2 mm wide, maximum thickness 0.10 mm.
- Specimens are formed into a lapped cylinder on a 13 mm mandrel and clamped vertically.
- Ignition source and burner
- Uses a calibrated 50 W small burner (ISO 10093 ignition source P/PF2); flame height adjusted to 20 mm ± 1 mm.
- Technical‑grade methane (≥98% purity) recommended for consistency.
- Test conditions
- Test atmosphere: 15 °C–35 °C and 45%–75% RH.
- Conditioning: two sets of five specimens at 23 °C, 50% RH (48 h) and at 70 °C (168 h) with desiccator cooling.
- Procedure and measurements
- Two successive 3 s ± 0.5 s flame applications with the burner tip positioned 10 mm ± 1 mm below the specimen edge.
- Record first and second afterflame times and the afterglow time; calculate total afterflame per specimen and set totals.
- Observe whether flaming/glowing reaches the 125 mm mark and whether the cotton‑wool indicator below the specimen ignites.
- Classification (informative Annex A)
- Optional category codes (e.g., VTM‑0, VTM‑1, VTM‑2) based on afterflame/afterglow limits and cotton‑wool ignition. Annex A is for quality control and preselection only.
- Limitations
- Intended as a comparative, small‑scale screening test - not a measure of full fire hazard or real‑world performance. Results depend on material formulation, thickness, colour, anisotropy and specimen orientation.
Applications and users
- Useful for:
- Material suppliers and compounders assessing fire‑retardant formulations.
- Quality control and in‑process verification for thin flexible plastic components (films, laminates, coatings).
- Product designers and R&D teams preselecting materials for applications with low‑energy ignition scenarios.
- Testing laboratories performing standardized small‑scale burning tests and comparative evaluations.
- Practical benefits:
- Rapid screening of changes in burning behaviour due to additives, pigments or processing.
- Objective data (afterflame/afterglow times) for material selection and specification drafting.
Related standards
- ISO 1210 - burning behaviour of horizontal and vertical specimens (50 W source)
- ISO 10093 - standard ignition sources (burner specification)
- ISO 291 - conditioning atmospheres for plastics
- ISO 1043‑1 - polymer symbols
- ASTM D5207 - calibration practice for small test flames
Keywords: ISO 9773:1998, plastics burning behaviour, thin flexible specimens, small‑flame ignition, afterflame, afterglow, vertical specimen test, fire testing, material classification.