The Vapour permeability of Adhesive films

 

Vapour permeability measurement is a critical parameter in relation to adhesive films across a range of industries. It determines how much vapour, usually water but other gases in some applications, can pass through a material over time, which directly impacts performance in applications where moisture control is essential.

 Industries Using Vapour-Permeable Adhesive Films


1. Medical and Healthcare

• Wound care dressings, surgical drapes, and transdermal patches need to allow skin to "breathe" while keeping out bacteria and moisture. A balance between breathability and barrier properties is essential to both the healing of the wound and the shelf life of the bandages.

2. Construction

• Vapour-permeable membranes and tapes in building envelopes allow internal moisture to escape, preventing mould and condensation, while blocking rain.

3. Packaging

• Used in food packaging (e.g., fresh produce) to control humidity inside the pack and prevent spoilage.

4. Electronics

• Used to encapsulate or seal components while allowing minimal vapour exchange to prevent condensation.

5. Textiles and Apparel

• Adhesive films in waterproof-breathable garments (e.g., for sportswear or outdoor use) allow sweat vapour out but keep rain out.

Key International Standards

Here are some internationally recognised standards relevant to vapour permeability of adhesive films:

• ASTM E96 – Standard Test Methods for Water Vapour Transmission of Materials (includes both desiccant and water method).
• ISO 2528 – Vapour permeability for flexible barrier materials, commonly used in packaging.
• ISO 15106 series – Covers various WVTR testing methods using different technologies (gravimetric, coulometric, etc.).
• EN 13726-2 – Used in medical fields, especially for wound dressings.
• BS 3177 – An older British Standard, still referenced for water vapour transmission in certain applications.

Method	Principle	Units	Typical Applications	Relevant Standards
Instrumental method	Numerous sensor types are available including mass spectrometry	g/m²/day	Woks well across all applications for material samples as well as components	Chris, what would you say are the main ones?
Coulometric Sensor (Modulated Humidity)	Detects water vapour passing through the sample using a sensor that quantifies moisture content in nitrogen gas.	g/m²/day	Barrier films in electronics, pharma packaging	ISO 15106-3
Infrared Detection (IR Sensor)	Measures the water vapour using an IR beam absorbed by moisture molecules in a test chamber.	g/m²/day	High-barrier packaging films, multilayer laminates	ISO 15106-2
Electrolytic Sensor	Vapour passes through film and is absorbed in phosphorus pentoxide, creating an electrical current.	g/m²/day	Pharmaceuticals, sensitive electronics packaging	ISO 15106-1
Dynamic Vapour Sorption (DVS)	Measures the change in mass as a film sample is exposed to different humidity levels in a controlled environment.	µg/s or % RH over time	Advanced materials research, high-precision measurements	No single WVTR-specific standard, but widely used in research
Gravimetric (Desiccant or Water Method)	Measures weight change over time due to vapour transfer across a film sealing a cup of desiccant (or water).	g/m²/day	Construction membranes, packaging, medical dressings	ASTM E96 (Desiccant & Water Method), BS 3177
Isostatic Humidity Cell (Upright Cup Test)	Variation of gravimetric method with fixed humidity on both sides and no desiccant.	g/m²/day	Membranes in textiles and breathable films	Often referenced in building codes, or derived from ASTM E96

Summary

Vapour permeability measurement of adhesive films is vital across many industries for controlling moisture without sacrificing barrier integrity. From medical devices to construction and food packaging, understanding and controlling this property ensures product safety, performance and comfort.