| Title |
A Study for Correlation between Gas Diffusivity and Molecular Kinetic Diameter in Gas Charged Polymer Specimen |
| DOI |
https://doi.org/10.3365/KJMM.2025.63.11.928 |
| ISSN |
1738-8228(ISSN), 2288-8241(eISSN) |
| Keywords |
Gas diffusivity; Molecular kinetic diameter; Diffusion analysis program; Volumetric analysis method; Manometric analysis method; Polymer |
| Abstract |
Polymer-based gas sealing technology is a key component to ensure the safety and reliability of
high-pressure gas systems, and it is essential for infrastructure such as hydrogen refueling stations. In
particular, the sealing performance of polymer materials used in O-rings varies depending on the gas diffusion
characteristics of each gas. This necessitates a quantitative analysis of diffusion behavior for major gases
including hydrogen, helium, nitrogen, oxygen, and argon. Hydrogen and helium have small molecular sizes
and high diffusion rates, allowing them to easily permeate through polymer materials, while nitrogen and
argon have slower diffusion rates, potentially affecting long-term sealing performance. In this study, five pure
gases (H2, He, N2, O2, Ar) with different molecular kinetic diameters were used to quantitatively analyze the
diffusion properties of four polymer materials (LDPE, HDPE, EPDM, NBR) under high-pressure conditions
ranging from 1 to 10 MPa. A combination of a volumetric-based gas release measurement method and a
pressure-based method was employed to precisely quantify the released gas volume, with compensation for
ambient temperature and pressure fluctuations. From these measurements, a quantitative relationship
between gas diffusivity and molecular kinetic diameter was established. The results showed that the
diffusivity of gases tends to be inversely proportional to the square of the molecular kinetic diameter,
consistent with predictions from the Chapman?Enskog diffusion theory. This study provides fundamental
data for the design of polymer sealing materials under high-pressure gas conditions and suggests broad
applicability across various gas industries, including hydrogen energy systems, semiconductor processing, fuel
cells and environmental control systems. |