Barrer

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A Barrer is a non-SI unit of gas permeability (specifically, oxygen permeability) used in the contact lens industry. It is a bulk property.

[edit] Definition

1 Barrer = 10^-11 (cm³ O₂ ) cm cm^-2 s^-1 mmHg^-1.

Here 'cm³ O₂' represents a molar quantity of oxygen rather than a true volume. It represents the quantity of oxygen that would take up one cubic centimeter at standard temperature and pressure, as calculated via the ideal gas law.
The 'cm' represents the thickness of the material whose permeability is being evaluated, and cm^-2 is the reciprocal of the surface area of that material.

1 Barrer = 846 millilitre . mm / (cm² . day. bar(a))

1 bar(a) = 1 bars absolute (with respect to vacuum)

[edit] External links

• How Dk is measured, and is there a certifiable standard? ('Dk' is an equivalent term to 'permeability'.)
• S. A. Stern, 'The barrer permeability unit', Journal of Polymer Science Part A-2: Polymer Physics,Volume 6, Issue 11 , Pages 1933 - 1934