GB/T 21332-2025 Active

This document describes the methods for measuring the water vapor permeability, water vapor transmission rate, water vapor transmission coefficient, and water vapor diffusion resistance index of rigid foam plastics.
This document is applicable to rigid foam plastics with a thickness of more than 10 mm. These can be self-skinned foam materials or foam materials adhered to different surface materials.
This document specifies three different temperature and humidity conditions:
a) 38°C, with a relative humidity gradient of 0% to 88% on both sides of the sample;
b) 23°C, with a relative humidity gradient of 0% to 85% on both sides of the sample;
c) 23°C, with a relative humidity gradient of 0% to 50% on both sides of the sample.
The results obtained by this method are used for product design, production control, and product specifications.
This method is applicable to materials with a water vapor permeability ranging from 3 μg/m2·s to 1,400 μg/m2·s.