AQUATRAN 3/38 Operator’s Manual
Preparing for a Test
MOCON, Inc.
Revision G
3-1
Chapter 3: Preparing for a Test
This chapter provides information on how to prepare for a permeation test.
Read this chapter to learn about:
•
Testing Basics
•
How Barrier Properties Affect Testing
•
Developing Test Methods for Films and Packages
•
Developing a Temperature Profile
Testing Basics
A permeation test is comprised of a series of discrete actions or events. Some of these steps require human
thought, action or intervention. Some of the steps are performed by the instrument and will be discussed
elsewhere. The most important part of the process is the planning and preparation that occurs before the
actual testing begins. Inadequate planning or preparation may result in an inaccurate measurement. This
chapter contains information on the factors that should be considered when planning for a permeation test.
How Barrier Properties Affect Testing
A good understanding of the barrier material properties for the samples to be tested is very helpful when
preparing for a permeation test. The transmission rate of the sample and the conditions at which it will be
tested may require changes to the test methodology.
Any sample with a transmission rate within the range of the instrument (as specified in Chapter 9) can be
tested. Additional consideration is advised when setting up tests for samples that have a transmission rate
within 25% of the upper or lower end of the instruments test range.
Use caution when testing at the upper end of the instruments test range, an excessively high transmission
rate will over-range the water vapor sensor. Common poor barrier materials include polyethylene,
polycarbonate and acrylic.
The possibility of an over-range condition can be reduced by; lowering the water vapor concentration (RH)
of the Test Gas, using a mask to reduce the area of the film samples or increasing the Carrier Gas flow rate.
Using any or all these methods will reduce the amount of water vapor in the carrier gas, reducing the
possibility of an over range condition.
Testing Mixed Barriers
Simultaneously testing barriers with widely divergent transmission rates is not recommended. The data for
some samples may not be accurate when there is a large difference in the transmission rates. If during a
test there is a large difference in the transmission rates, set the divergent cell (or cells) to Idle and continue
testing the remaining cell (or cells). You may want to determine which samples will condition more rapidly
and test those samples first.
