TM 1-1500-204-23-11
locally fabricated from plastic pipe, a clear Plexiglas
pipe. Wrap all male itting threads with pipe sealing
plate, vacuum bag sealant tape, the connector from
tape, A-A-58092. See igure 3-25.
a vacuum valve assembly and a piece of threaded
Figure 3-25. Vacuum Cup
g. Wiping Cloths. Wiping cloths must be low lint
paper must not be coated with wax or oil. Barrier
and manufactured from material free of contaminates
paper or vacuum bagging materials may be used in
such as cotton seed oil, fabric sizing, lame retardant
lieu of kraft paper.
chemicals, and silicone. Cloths conforming to AMS
3819, Class 1, 2 or 3, Grade A and Federal Spec-
NOTE
iication CCC-C-46 Type 1, Class 7, have passed
Desiccant can be reactivated by drying in an
solvent extraction, linting, and silicone contamination
oven at 150 to 200 F until the color change
tests and are acceptable. Do not use other types,
is reversed.
classes or grades for adhesive bonding applications.
j. Moisture Indicator. The moisture indicator is
NOTE
used to determine if a part is dry following the
Isopropyl alcohol must be reagent grade or
composite honeycomb sandwich part drying cycle
technical grade due to the unacceptable water
speciied in Chapter 6. It uses a color changing
content in lesser grades.
desiccant to indicate the presence of moisture. The
indicator consists of vacuum valve couplings, an
h. Solvents. Always use the purest grade of sol-
airline ilter, color changing desiccant and rymple
vent available; order of preference is: reagent grade
cloth. It is essential that the desiccant consist of
(A-A-59282); technical grade (same as commercial
calcium sulfate containing cobalt chloride as this is
grade); and general purpose. Acetone and isopropyl
the ingredient that causes the blue to pink color
alcohol are suitable solvents for surface preparation
change indicating the presence of moisture. Use of
for adhesive bonding of advanced composites. Methyl
a desiccant material without cobalt chloride will result
Ethyl Ketone is suitable; however, it is being phased
in a false dry indication. The desiccant must be fresh
out due to environmental concerns. Only use wash
and blue in color prior to use. Replace the desiccant
bottles designed for the particular solvent being used.
after each use. Maintain the desiccant in a moisture
Other types of plastic bottles may leach plasticizer
proof sealed container. See igure 3-26.
out and contaminate the bonding surface.
i. Kraft Paper. Kraft paper is used to protect
precured patches and parts from contamination. The
