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I have done a permeability experiment on LDPE in the presence of air using a 25mm circular specimen. At 30'C, the permeability was found to be 1.846 barrer.

enter image description here

Now I am trying to apply this permeability value to a calculation whereby I am trying to find what the change in pressure of a dunnage bag is (it is a bag that has the shape of a pillow) after 5 minutes. I have the following info of the dunnage bag:

  • Volume of bag = 0.2064 m3 (This was calculated using the Paper Bag Problem)
  • Approximate area = 1.35 m2 (this is just a quick approximate)
  • Thickness of LDPE = 0.042 x 10-3 m
  • Time = 5 x 60 s = 300 s

Is it correct if I convert barrer to SI units in the following manner:

1 barrer = 7.5005 x 10-18 m2s-1Pa-1

By using the following formula, I was hoping to calculate the change in pressure. However, my values don't make sense at all!

$$\text{Permeability} = \dfrac{\text{Volume}\cdot\text{thickness}}{\text{Area}\cdot\text{time}\cdot\text{Change in Pressure}}$$

Wasabi
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I.vdM
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  • I improved your formatting, including your equation at the end. However, given you didn't use parentheses to make what was dividing what explicit, I recommend that you take a look to see if I did it correctly. If not, feel free to [edit] your question as you see fit. – Wasabi Apr 28 '18 at 00:29

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