TM 1-1500-204-23-11
during mixing. If lat end stick is unavail-
able, one can be created by cutting the
end off a rounded stirring stick.
Apply pressure to layup within the pot life
listed by the manufacturer.
For ambient
temperatures in excess of 90 F, decrease
Inadequate mixing will result in poor structural
this time by 50%. An unsatisfactory repair
performance. Do not whip resin when mixing
will result if the resin gels before adequate
but gently fold over the material to minimize the
pressure is applied.
introduction of air into the mixture. Trapped
air causes excessive porosity and thereby
Select heat blanket (if required) and all nec-
reduces the strength of the bonded repair.
essary vacuum bag materials prior to mixing
Solvents shall not be used to aid in mixing
resin.
adhesives and sealants. Bonding is degraded
when solvents are used to thin adhesives.
NOTE
Use clean wax free cups to mix resin. Cut
(h) Mixing is complete when the resin
the end of a tongue depressor square to mix
shows uniform color and viscosity
the resin so the stick can reach the corners
throughout its total volume.
of the cup.
(i)
When mixing is complete, record the
time to indicate the start time of the
(a) Remove the containers of resin from
resin s pot life as adhesives start to cure
storage. If containers are in refrigerated
when mixed.
storage, allow material to reach room
temperature before opening. Ensure
d. Vacuum Degassing Vacuum degassing of
material has not exceeded its shelf life.
adhesives may be needed to remove or eliminate any
entrapped air that may cause voids in the product.
(b) Place a piece of release ilm down on a
Follow these steps to perform vacuum degassing:
workbench and position the scale.
(1) Place the mixed material that is to be
(c) Ensure the cups used will be capable of
degassed in a degassing chamber.
holding the total resin amount required.
Label each cup with the resin compo-
nent it will be illed with and batch num-
ber (e.g. Part A-1).
The material may foam and expand rapidly
(d) Weigh the mixing cups for each compo-
and overlow the container. During this frothing
nent. Record the weight of each cup.
process, it may be necessary to disconnect
and then reconnect the vacuum as needed
(e) Place the proper amounts of base, cur-
to prevent the material from overlowing.
ing agent, and iller, if required, in its cor-
responding mixing cup. Remember to
(2) Connect the vacuum
source
to
the
subtract the weight of the cup to deter-
degassing chamber.
mine the amount of material in the cup.
A stirring stick can be used to aid in
(3) The entire degassing process usually can
pouring very thin components.
be completed within 5 minutes from the time
this frothing process stops. The degas time
(f)
When ready to impregnate the fabric,
should not exceed one quarter of the pot life
pour the curing agent (Part B) into the
of the material.
corresponding base (Part A) container.
(4) When pouring the mixture into the mold, do
Also pour in the iller material if required.
not stir or fold the material, which could lead
Remove as much of the material, from
to air reentering the material.
the cup as possible. Use separate lat
end stirring sticks for each application.
e. Liquid Shimming. Fit up gaps and mismatches
between two adjoining parts can be sometimes met by
(g) Mix thoroughly using a new lat end stir-
applying and curing a liquid shim between the parts.
ring stick being careful to minimize the
Generally, liquid shim should not be any thicker than
amount of air introduced into the mixture
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