Measurement Techniques for Permeability of Gases and Vapors Through Polymer Films

Permeability is a crucial property for various polymer film applications, including packaging, medical devices, and protective coatings. It signifies the ability of a material to allow gases, vapors, or liquids to pass through its structure. This report explores two standard methods for measuring the permeability of oxygen, carbon dioxide, water vapor, and organic vapors through flat polymer structures: the continuous-flow method and the lag-time method.

The American Society for Testing and Materials (ASTM) International provides standardized procedures for permeability measurements. ASTM D 3985-81 outlines the method for measuring oxygen and carbon dioxide gas permeability, while ASTM E 96-80 details the measurement of water vapor permeability. Permeability of organic vapors is often determined using similar principles, with commercially available equipment from companies like MAS Technologies Inc. and Modern Controls Inc.

C403H Oxygen /Water Vapor Transmission Rate Test System is based on the testing principle of Coulometric oxygen sensor and infrared water vapor sensor. It is designed and manufactured according to ASTM D3985、ASTM F1249，ISO 15106-2

C360H Water Vapor Transmission Rate Test System, is designed and manufactured based on the gravimetric determination method and conforms to the requirements of ASTM E96.

Continuous-Flow Method

This technique involves exposing one side of a polymer film sample to a constant flow of the permeant gas or vapor. The permeant diffuses through the film, and the permeation rate is measured on the opposite side. Fick's second law of diffusion governs this process, and its solution allows for the calculation of the diffusion coefficient (D) and permeability coefficient (P) based on the flow rate data. Equation (2) provides a simplified approach to calculate D based on the time required to reach a specific fraction of the steady-state flow rate (Fss).

Lag-Time Method

This method utilizes a different approach. The polymer film sample initially contains no permeant. One side is then exposed to a constant concentration of the permeant gas or vapor. The permeant accumulates in the film and then diffuses through it. The lag time (θ) is the time it takes for the permeant to reach the opposite side and be detectable. Equation (7) relates the lag time to the diffusion coefficient.

Data Analysis and Interpretation

Both methods involve analyzing the obtained data (flow rate vs. time for continuous-flow and permeant concentration vs. time for lag-time) to calculate the relevant parameters. The continuous-flow method often utilizes linear regression techniques to determine the slope for calculating D. The lag-time method relies on identifying the intercept of the steady-state line with the time axis to obtain the lag time (θ).



The continuous-flow and lag-time methods offer valuable tools for characterizing the permeability of gases and vapors in flat polymer structures. Choosing the appropriate method depends on factors like desired sensitivity and experimental setup. Both techniques rely on established mathematical models like Fick's second law of diffusion for data analysis and parameter calculation. Understanding these methods is essential for selecting suitable polymer materials for various applications with specific permeability requirements.



As the demand for functional packaging materials grows, testing methods are evolving to ensure a more comprehensive evaluation of packaging films. Labthink encourages collaboration with packaging industry companies for quality control! Visit the website www.labthink.com to learn more!