Q: Do you have a reference material that gives the same WVTR with each of these four methods at the low end? How well do the methods correlate?
A: No, our reference films are designed to fit into our Aquatran’s 50cm2 diffusion cell.
Q: What source of carrier gas do you use as to not measure external moisture?
A: Nitrogen Gas that we use comes from liquid nitrogen which is very pure. We also use a very high purity dessicant before the gas enters the instrument.
Q: What is the life span of the coulometric sensor? How often do they need to be replaced?
A: Through my experience with them it’s about 2-5 years. The one sensor that did loose efficiency after 2 years however, I suspect the lower life was due to testing some very high level WVTR films that were technically above the limit of the instrument.
Q: Do you have a reference film to confirm calibrations for the Aquatran?
A: Yes, films do come with the instrument.
Q: How long do you have to run that individual zero?
A: Until you are satisfied that it’s low enough. In our lab, we’re looking for a 1% change or less over 24 hours or +/- the low end of the instrument (0.5 mg/ (m2 day) over 24 hrs.
Q: How do you deal with edge effects when ambient O2 or H2o could reach the det. at similar rates as the permeation rate?
A: You would run an individual zero (nitrogen on both sides of the film) first, to subtract any edge permeation from ambient.
Q: For films with barrier at transmission rates of 0.006g/m2/day what calibration standard should be used for my Aquatran?
A: We would verify the instrument with our low-end (Green) NIST cert film. The low end NIST film level is aproximately 0.18 mg/day, No calibration needed, just verification to insure instrument is working correctly. The instrument uses an absolute coulometric sensor.
Q: Is it reasonable to expect that I can use JIS standard cup testing with CaCl2 as a desiccant to calibrate my MOCON when testing high barrier flat films for MVTR?
A: Cup testing high barrier films will take months for the levels that can be tested on our Aquatran. In many cases, the leak rates of traditional (twain Albert) type cups is higher than the films themselves. Additionally, you will need to have a lot of trust with your environmental chamber to hold temp and RH accurately for such a long time. MOCON doesn’t recommend this.
Q: Does Aquatran come with the test chamber (shown in your presentation) for small samples?
A: It does not come with a chamber, but could be added on as an accessory item.
Q: Can sensitivity be increased by allowing sample accumulation?
A: Theoretically, yes. Practically speaking, maybe not. One key issue is that water is a very “sticky” molecule. So flushing such a small amount of water efficiently from a cell and quantifying the peak is challenging because if accumulated, the water would stick to the walls of the cell and might take hours to fully come off. The Aquatran is not set up to be an accumulation type device.
Q: To improve sensitivity can the flow thru rate be operated so low that it is in quasi-accumulation mode but is still continuous?
A: Good question. Unlike the WVTR instruments (where the concentration of water is measured by the IR detector), the Aquatrace sensor analyzes all of the water, so sensitivity isn’t improved with lower flow rates. The sensor itself currently is better than the instrument and the challenge for us is to make a tighter instrument, larger cells, etc.
Q: Can you show the time to reach steady state, typically?
A: The uptake curve in one of the graphs on the presentation (comparing Aquatran with the 3/33 instrument) is a typical example. (See presentation slides)
Q: How accurate is this method compared to the conventional methods? Are there less error sources?
A: You may contact a Sales Rep for the specific specs of the instrument. As an example, we have NIST films for verifying the precision and those have a certain allowable precision. The instrument should always perform within this spec.
Q: What do you think about WVTR or OTR determination thanks to a chromatography when you test an active barrier packaging (with O2 scavenger/desiccant) compared to the MOCON system?
A: Scavengers are always an interesting subject. Initially (for a perfect scavenger), the TR should be zero. As it’s depleted, the TR will rise and once fully depleted, then equilibrate. Depending on the scavenger type, dispersement within the polymer and its efficiency, one will see varying TR results. Often it’s nice to characterize the sample throughout its usable life (months to years). However, this would involve locking up the instrument for that time. In this case, one would continue conditioning the sample off-line and periodically place it back on the instrument for interim TR results.
Q: You mentioned that you could test a small device that has water in it. What about a larger device? What is the limit?
A: We would need to review the devices on a case by case basis. In many instances, we’re only limited by our imagination. Ideally, the capture vessel holding the device will be made to allow for as little volume as possible, to allow the carrier gas to sweep the chamber in an efficient manner.
Q: If you over range the sensor does it clear like the ox-trans?
A: Yes. It has the same type of built-I safety mechanisms that shut-off the test and purge the sensor. As in an OxTran, it will take a day or so to fully recover for low transmission rate testing, if you really do over-whelm it.
Q: Does special diffusion cells for blister cavities exist, or is it the same for flat films?
A: We do have special blister cavity cells that we’ve used for years on our Permeatran 3/33 instruments. I have successfully used them on our Aquatran instruments. They replace the standard cell head and work well.
Q: What is the sensitivity of the Aquatran?
A: The low end of the Aquatran is 0.5 mg/ (m2 day) or 0.0005 g/ (m2 day).
Q: Does the P2O5 sensor a shelf life?
A: Every instrument and sensor is checked out before we ship them. So you will never receive an old sensor from us. As for the life of the sensor, we warranty the instrument for one year. In my lab, I have had sensors last for 5+ years. However, I do limit the testing to low WVTR samples. Since this is a chemical sensor, if one does routinely expose it to high WVTR samples the life time would be less.
Q: What is the purpose of Tritium testing other than HTO detection? What materials or products require this type of test?
A: There are many papers on this topics and a quick internet search should help you. On the presentation of this method there is a good footnote for information as well
(Arrelaine A. Dameron – Understanding moisture ingress and packaging requirements for photovoltaic modules). Tritium is considered a good replacement to H2O, due to its similarities, scarcity (i.e. no noise from ambient humidity), and a relative ease for testing. One is essentially counting the radiation of Tritium. However, many hazards and precautions are needed, it’s expensive equipment to set-up and it’s limited (as far as I know) to film testing.
|
