Q: Will it be possible to obtain an experimentally negative transmission rate?
A: No, but you might see negative numbers on a permeation instrument but does not mean that it is negative. Usually it is wrong and you should re-test.
Q: Masking is needed for smaller sample, what are the type of mask available?
A: There are several types and sizes of masks available to purchase. You may contact MOCON to get a list of masks and prices.
Q: If we have the individual permeability of 2 layers, how can we calculate the permeability of the total laminated structure?
Q: Do you have one piece of equipment that measures both WVTR & OTR?
A: Due to the specific sensitivity of the sensor system we only provide seperate instrumentation.
Q: You mentioned that one of the variables that affect the permeability is Permeant concentration. Could you relate this factor with the pressure of the permeant (gas)?
A: Partial pressure only. Permeation is only partial pressure of O2 from one side vs. the other side.
Q: What is the Unit of Driving force?
A: The driving force is usually the partial pressure and common units are: mil. of mercury, psi, cm Hg,
mm Hg, etc.
Q: How do you decide the standard flow for permeation for eg. 10sccm or 100 sccm?
A: This is based on the sensors and what you are measuring. All instruments are different.<
Q: Is the unit of q in moles ?
A: The amount or quantity is in cc’s.
Q: I have seen permeability as product of diffusivity and concentration with units of conc. being mol/liter. Is that right?
A: Not concentration. I would say solubility would equal mol/liter.
Q: In case of paperboard laminate or coated paper will the water transmission rate be a function of porosity of paper, solubility & diffusivity of water with paperboard?
A: Yes, the coated paperboard has to be coated to get any reliable results. It is very easy for water to get to the paperboard if not properly coated and it is then hard to get accurate results.
We do have special test cells just for this material because it is so unique.
Q: There are different methods of testing WVTR: gravimetric and the way Mocon tests with help of carrier gas. How can we relate the results of Gravimetric method to the Mocon tested results?
A: You can relate the TR of each test to each other but you have to know your driving force. The reason the instrument method was created though is because of the inconsistencies of the Gravimetric method.
Q: What about the reverse flow of N2 from the detecting side?
A: It doesn’t really matter. O2 will still move, the amount of gas doesn’t ever get so much to where it wont travel through.
Q: Does the measurement system address the defects in the sample?
A: Not really. Usually you’re testing only a small sample of the product, some samples may be fine and others may have defects, which means you will be getting different numbers. It is best that after you do testing on your samples you also test the finished package or product to determine any actual defects with the product as a whole.
Q: We had tested ALU /Alu film on Mocon theoretical WVTR Instrument. The value should be zero but we get negative value?
A: Typically this would happen because your initial zeros are too big, or you have pin holes in the product you are testing.
Q: what is mean by S & D Value?
A: The solubility and diffusion rate mean how much of the gas your package can hold.
Q: With produce packaging a lot of perforated film is being used to reach equilibrium. Can permeability be accurately established for oxygen transmission and WVTR rates?
A: Yes, but it is more difficult. Because of this packaging you can not introduce total pressure. For this you will have to go through lab testing for accurate results.
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A: It will be an equation like: 1 = 1 + 1 and so on.