ISO 22007-4:2024

Overview

ISO 22007-4:2024 specifies the light flash method for determining the thermal diffusivity of thin plastic discs in the thickness direction. The method measures the transient temperature rise at the rear face of a specimen after a short, uniform energy pulse on the front face. It applies to homogeneous plastics and composites with isotropic or orthotropic structure and supports measurements from −100 °C to +400 °C for materials with thermal diffusivity in the order of 1×10−7 to 1×10−4 m2·s−1. The standard replaces the term “laser flash” with the broader “light flash” and includes requirements for apparatus, specimen preparation, calibration, data analysis and uncertainty assessment.

Key topics and technical requirements

• Principle: Record the rear-face thermogram produced by a short light pulse and derive thermal diffusivity by comparison with theoretical models (see Clause 9 and Annex B).
• Specimen: Thin disc geometry (typical diameters 5–20 mm; thickness commonly 0.5–3 mm), flat parallel faces, diameter-to-thickness ratio > 3:1; thickness measured to ±5 µm (resolution ±1 µm).
• Apparatus: Furnace or climatic chamber with optical windows, flash source (laser or flash tube), pulse detector, IR transient detector, specimen holder and data acquisition/analysis unit.
• Detector & acquisition: IR detector sensitivity ~5 mK, linear over ≥3 K, frequency response faster than 10 kHz; record thermogram with >1 000 data points and sampling rate adequate relative to the half-rise time.
• Pulse & heating: Pulse duration < 1 ms; rear-face temperature rise normally ≤ 3 K to avoid nonlinear effects.
• Environment & temperature control: Tests may be performed in gas or vacuum (vacuum minimizes convection); chamber stability ±0.5 K and temperature measurement accuracy ~±0.5 K.
• Quality controls: Calibration and verification routines, specified specimen conditioning (ISO 291), uncertainty estimation (GUM/ISO/IEC Guide 98-3), and reporting requirements.

Applications and users

• Who uses it: Materials scientists, polymer engineers, quality control and testing laboratories, R&D teams, and standards bodies assessing thermal properties of plastics and polymer composites.
• Practical applications:
  • Thermal characterization for electronics packaging, automotive and aerospace components
  • Material selection for insulation, heat sinks, and thermal interface materials
  • Verification of processing effects (orientation, anisotropy) on thermal behavior
  • Inputs for thermal modeling and simulation (thermal diffusivity → conductivity via density and specific heat)

Related standards

• ISO 22007-1 - General principles for determination of thermal conductivity and diffusivity
• ISO 291 - Conditioning and testing atmospheres for plastics
• ISO 527-1 - Tensile properties (relevant for specimen preparation)
• ISO/IEC Guide 98-3 (GUM) - Guide to the expression of uncertainty in measurement

Keywords: ISO 22007-4:2024, light flash method, thermal diffusivity, thermal conductivity, plastics testing, polymer thermal properties.