ALTANA BYK-Gardner Permeability Cup - Manual (Page 5)

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Where an adsorbent is specifi c for a given gas
(e.g., ascarite readily adsords carbon dioxide),
the permeability of fi lms to this gas can also be
determined by placing adsorbent in the cup and
keeping the cup in an atmosphere of the gas in
question.
Because the rate of vapor or gas permeation is
very dependent on temperature, the more precise
the temperature control during the test period, the
more accurate and reproducible will be the test
results.
SAMPLE PREPARATION:
Uniform unsupported fi lms of lacquer, enamel
or varnish can be obtained by coating polished
tinplate with those materials, allowing to cure, then
stripping by mercury amalgamation of the tinplate.
The method of application should be stated in all
cases and should be the same for materials which
are to be compared directly.
Coating materials too brittle to be handled as
free fi lms should be coated on a porous support,
such as a dializer parchment, paper or glass
cloth. The desired number of coats should be
applied allowing the correct drying time for‘ each
coat. The drying time and the manner of drying
should be reported. The time interval between
drying and testing can be varied depending on
the information desired, but this interval should be
recorded.
Description