ASTM F392
DURABILITY OF FLEXIBLE BARRIER MATERIALS (GELBO FLEX CONDITIONING)
Standard Practice for Conditioning of Flexible Barrier Materials for Flex Durability
Where Used
Gelbo Flex testing creates a repeatable method for stressing materials and is often used as a “worst-case” simulation method for understanding the potential film “wear and tear” due to processing and shipping.
Historically, materials conditioned with this method were tested for through-hole/pinhole defects. However, with the improvements of multilayered polymers, through-holes are less common, and this material conditioning is most often used to understand how gas barrier characteristics (oxygen transmission rate and water vapor transmission rate) are impacted by the stresses applied to the material.
Description
This test method flexes materials at standard conditions. The flexing action consists of a horizontal motion (compression) along with a twisting motion (440° twist in the first 3.5 inches and then a horizontal motion to finish the compression). This compression/twisting motion is repeated multiple times.
- Flexing action consists of a twisting and crushing motion following conditions A to D.
- Condition A – full flex for 1 hour (2700 cycles)
- Condition B – full flex for 20 minutes (900 cycles)
- Condition C – full flex for 6 minutes (270 cycles)
- Condition D – full flex for 20 cycles
- Condition E – partial flex only for 20 cycles
- For more details about ASTM F392, please visit the ASTM website.
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Instrument Utilized: Gelbo Flex Tester
This method of conditioning can be very severe. The most common test condition for typical “wear and tear” is Condition D.
To be conditioned, the film samples are 8 by 11 inch flat sheets.
For understanding the flex conditioning effects upon permeation testing, it's best to compare both "flexed" and "pristine" film samples.
Download the Note on Gelbo Flex Conditioning