ISO 22007-6:2014

Overview

ISO 22007-6:2014 specifies a comparative modulated-temperature method for measuring the thermal conductivity of plastics with low thermal conductivities. The standard defines a temperature-modulation technique using a Peltier-type heat source and a double lock-in amplification to measure very small temperature oscillations (input deviation < 1 K). It is intended for low-conductivity materials in the approximate range 0.026 W·m⁻¹·K⁻¹ to 0.6 W·m⁻¹·K⁻¹, minimizing radiation and convection errors and allowing measurements on small specimens.

Key topics and technical requirements

• Principle: A thin probe material (sheet) is placed between a modulated heat source and the sample. Two sensors measure amplitude of temperature modulation at x = 0 and x = d; the decay ratio (gain) is used to infer thermal conductivity in a thermally thin condition (kd << 1).
• Temperature modulation: Small amplitude oscillation (typically less than ±1 K) with the average temperature kept constant using a Peltier thermo-module.
• Signal detection: Use of thermopile sensors and a double lock‑in amplifier system to amplify and extract small temperature signals from noise.
• Apparatus requirements:
  • Large heat sink to stabilize baseline temperature.
  • Peltier thermoelectric module as a modulated heat source (example size 30 mm × 30 mm).
  • Two sensors (example thermopile area ~5 mm × 2 mm) placed at front and rear of the probe.
  • Heating and measurement electronics sized to obtain high signal-to-noise ratio.
• Probe and specimen geometry:
  • Probe thickness chosen relative to the thermal diffusion length (k = (ω/2α)1/2).
  • Probe materials with similar thermal properties to samples are preferred (e.g., cast PMMA sheet 0.5 mm).
  • Specimen area comparable to the Peltier module for near one-dimensional heat flow.
• Calibration/comparison: Thermal conductivity is determined by correlation between thermal impedance and amplitude decay using two reference materials measured at the same frequency and temperature.

Applications and users

• Practical for measuring low thermal conductivity plastics and cellular foams where traditional steady-state methods are impractical.
• Ideal for small or micro-scale specimens: packaging trays, thin films, gelling sheets, adhesives, thermal interface materials, electronic component substrates.
• Primary users: materials testing laboratories, plastics manufacturers, thermal characterization and R&D teams, quality control engineers, and certification bodies involved in insulation and thermal management.

Related standards

• ISO 22007-1 - General principles (Plastics - thermal conductivity/diffusivity)
• ISO 22007-3 - Temperature wave analysis method
• ISO 22007-4 - Laser flash method
• ISO/TR 22007-5 - Interlaboratory test results (PMMA)
• ISO 472, ISO 80000-5 (terminology and units)

Keywords: ISO 22007-6:2014, thermal conductivity measurement, temperature-modulation technique, plastics testing, low thermal conductivities, Peltier module, lock-in amplifier.