ISO 21232:2018

Overview

ISO 21232:2018 specifies a laboratory test method to assess the moisturizing effect of textile materials by simulating the microclimate between textiles and human skin. Using a sweating guarded-hotplate (per ISO 11092) plus a purpose-built spacing device and humidity sensor, the method measures water‑vapour resistance including the air layer (Ret_al) and relative humidity (RH) in the air gap between a simulated skin surface and the specimen. The procedure applies to fabrics, films, coatings, leather and multilayer assemblies used in clothing systems.

Key Topics and Technical Requirements

• Principle: Simulate the skin–textile microclimate to evaluate how textiles retain or impede moisture evaporation and therefore influence skin hydration.
• Primary measurements:
  • Water‑vapour resistance including air layer (Ret_al) - expressed in m²·Pa·W⁻¹.
  • Relative humidity (RH) within the microclimate.
  • Hydration value of the non‑porous hydrophilic membrane (measured by hydrometer/Corneometer® method) used to simulate skin moisture.
• Apparatus:
  • Sweating guarded-hotplate conforming to ISO 11092:2014.
  • Device including a temperature and humidity sensor positioned between hotplate and specimen; sensor accuracy ±2% RH, ±1 °C.
  • Non‑porous hydrophilic breathable membrane (≈10–30 µm thick) with a hydration value of 45 ± 5.
• Test conditions and specimen preparation:
  • Condition specimens at (20 ± 2) °C and (65 ± 4) % RH according to ISO 139.
  • Test environment: measuring unit and air at 35 °C, ambient RH 40 %, air speed ≈1 m/s.
  • Mount specimens over the membrane using the specified frame and magnets; wait for steady‑state readings.
• Reporting: Results must include specimen identification, number of specimens, conditioning atmosphere, average and coefficient of variation for Ret_al and RH, and any deviations from the procedure.

Applications and Who Uses ISO 21232:2018

• Textile manufacturers and R&D teams evaluating functional finishes (e.g., moisturizing finishes, encapsulated actives).
• Apparel designers for performance clothing (sportswear, thermal garments) where skin comfort and moisture balance are critical.