Permeation Rate Measurements of Ultra Barriers Using Cavity Ring-Down Spectroscopy
Barrier-quality advancements of various materials have pushed the sensitivity limits of commercially available water vapor permeation equipment. There is a need for techniques to test the next generation of Ultra Barriers.
There are emerging technologies for markets such as packaging, construction / habitat, healthcare, electronics, energy.
We need a barrier measurement technique that is:
- DL = 10-6 g/(m2-day)
Comparison of WVTR Techniques for Ultra Barriers
Cavity Ring Down Spectroscopy (CRDS)
The key to our Ultra Barrier test is the CRDS (Cavity Ring Down Sensor). In this sensor, a pulsed laser is directed into a cavity capped with partially reflective mirrors. This allows an extremely long path of many kilometers for the laser energy to be absorbed by a few molecules of water or oxygen. The detector is capable of sensing water vapor presence as low as 0.4 ppb.
The permeation rate of a material is determined by the rate of decay of light intensity over time. The lower the permeation rate, the longer it takes to absorb and decay the laser energy.
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