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Theory of Operation
Factors that Affect the Transmission Rate of a Barrier Material
The oxygen transmission rate of barrier materials is affected by several factors:
Barrier test temperature
•
Test gas (oxygen) concentration effect on driving force
•
Barometric pressure effect on driving force
•
Barrier Temperature
The temperature at which the barrier is tested has a great effect (usually logarithmic) on transmission rate.
This makes temperature one of the most important test conditions for most barrier materials. Many barriers
exhibit a 6% to 15% rise in oxygen transmission rate for each degree C rise in temperature.
Test Gas Driving Force
The driving force of the test gas has a direct effect on the oxygen transmission rate. The driving force of the
test gas is affected by the oxygen concentration of the test gas and the ambient Barometric pressure.
Barometric Pressure
Barometric pressure has a proportional effect on the oxygen transmission rate of a specimen due to the
increase/decrease in the density of the test gas.
The instrument automatically compensates all transmission rate data to sea-level pressure (760 mmHg).
Due to the wide potential variation in altitudes, reproducibility between laboratories may not be possible
unless the transmission rate data is compensated to sea-level pressure. The instrument compensates all
transmission rate data to sea-level pressure using the following ratio:
D-2
Standard
barometric
Ambient
barometric
Revision J
OX-TRAN Model 2/28 Operator's Manual
pressure
(760mmHg)
pressure
MOCON, Inc.
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