Permeation Accessory for the Micro-Chamber/Thermal Extractor
Permeation testing: Use of barrier materials
Barrier materials are often used within products to prevent or mitigate potentially harmful emissions from other materials. For example:
- Vehicle seat coverings are used to prevent VOCs from PU foam affecting IVAQ (In-Vehicle Air Quality)
- Food packaging film is used to prevent oxygen or VOCs from tainting foodstuffs
- Protective clothing (gloves, suits, etc.) to prevent against harmful chemicals e.g. chemical warfare agents
- Membranes are used in vehicle fuel systems to prevent the loss of fuel vapour
Standard methods requiring permeation testing
There are a number of international standards that require a permeation measurement to be made (e.g. EN-374-3 / ASTM F739 for glove permeation testing, ASTM F739-99a for permeation testing of protective clothing, ISO-15105-1,2 / ASTM F 1307-02 gas transition rate measurement for plastic sheet/films).
However, in many case, the setup of the required apparatus is complex and expensive and will only test one material at a time.
The test objective in all these methods is the same - that is, to evaluate the breakthrough time and rate of permeation for a test compound (usually a liquid or gas) through a test material (e.g. a latex glove).
Permeation accessory for Micro-Chamber/Thermal Extractor (µ-CTE)
The Markes permeation accessory is a proprietary accessory for the Markes Micro-Chamber/Thermal Extractor (µ-CTE) to enable permeation testing to be carried out on up to six material samples simultaneously. This is typically carried out at ambient or near ambient temperatures, however it is also possible to test at temperatures up to 120°C.
The accessory consists of a membrane pan retainer and septum. A section of the material to be tested is stretched over the membrane pan and secured. A small droplet of test compound is placed in a well at the bottom of the permeation accessory by injecting through a septum. The test material does not come into direct contact with the test compound.
The complete assembly is then placed inside one of the µ-CTE micro-chambers, and clean air is passed over the surface of the stretched material in each micro-chamber. Permeation of the test compound through the stretched material is assessed by monitoring the air exhausting from the micro-chambers using sorbent tubes and TD-GC/MS analysis in the normal way.