Technical data
and lubricants; but it has only fair weathering characteristics.
Because it is an epoxy, this coating is difficult to remove with
standard paint removers.
6.12.6.2 Uses. As a tiecoat over existing coating sys-
tems for the reapplication of MIL-PRF-85285 polyurethane
topcoat on the exterior of painted aircraft and other aerospace
equipment.
6.12.6.3 Mixing. Thoroughly agitate components (Ep-
oxy Resin Base Component A and Polyamide or amine resin
curing agent Component B) preferably with a mechanical
shaker prior to mixing. If required pour into separate mea-
suring or metering containers. Using manufacturer’s direc-
tions, mix equal volumes of the components A and B by
pouring B into A and thoroughly agitating. Best mixing
results can be achieved with a mechanical shaker. Mix only
materials from the same manufacturer, and do not mix more
material than can be used in a 4-hour period. After mixing,
allow the primer to stand 30 minutes before applying. This
primer must be agitated continuously during spraying appli-
cations to prevent settlement of pigment and ensure unifor-
mity of color. If in-1ine or in-head proportioning equipment
is used to mix base and catalyst (curing agent) as the paint is
being used, a 30 minute dwell time is not required before
application.
6.12.6.4 Thinning.
• MIL-T-81772 is flammable and moderately
toxic to eyes, skin, and respiratory tract. Eye
and skin protection required.
• PCBTF, NSN 6850-01-399-0676, is combus-
tible and an irritant to eyes, skin, and respira-
tory tract. Eye and skin protection required.
Disposable 8 mil nitrile gloves, splash
goggles, tyvek/cloth coveralls are the recom-
mended PPE. Use in well ventilated areas.
In areas where air quality regulations restrict
volatile emissions, do not add thinner MIL-T-
81772 to the primer coating as that addition may
raise the VOC content to greater than 340 g/L
(2.8 lbs/gal).
NOTE
PCBTF, NSN 6850-01-399-0676 is exempt as a
VOC or HAP by the EPA and by 48 states and
will not change compliance of high solids coat-
ings to air quality regulations.
The viscosity of the unthinned tiecoat may range up to a
maximum of 40 seconds in a No. 4 Ford Cup (56 seconds in
a No. 2 Zahn Cup). Strain the tiecoat through clean cheese-
cloth, per CCC-C-440, Type I, Class 2 or a commercial paint
strainer; and when required, adjust the viscosity by thinning
to a viscosity of 8 to 19 seconds in a No. 4 Ford Cup (17 to
23 seconds in a No. 2 Zahn Cup). Use thinner per MIL-T-
81772 Type II or PCBTF (NSN 6850-01-399-0676) Add
MIL-T- 81772, Type II thinner as required to achieve the
viscosity range above. In areas where air quality regulations
restrict volatile emissions, thin with PCTBF using up to 10%
by volume as a recommended maximum for reduction of
viscosity.
6.12.6.5 Application. Apply one coat of tiecoat to a dry
film thickness of 0.6 to 1.8 mils, (0.9 to 2.6 mils wet film).
Allow a minimum of five hours air dry at 75° F and ten hours
at 60° F before application of topcoat. After 8 hours at 75° F,
solvent wipe per Chapter 3 to reactivate before topcoating.
Since this epoxy tiecoat has a very high solids content, cross
coating may not be required; and the spray gun must be kept
moving to prevent excessive film build-up with subsequent
reduction of adhesion. Apply a topcoat within 24 hours of
primer application. After 24 hours, scuff sand the entire
primed surface with A-A-58054, Type I, Grade A abrasive
mat and solvent wipe the area per Chapter 3 prior to
topcoating. Discard any of this tiecoat mixed for longer than
the four hours pot life at 75° F. Higher or lower temperatures
shorten or lengthen the pot life proportionally.
6.12.6.6 Drying Time. The times given here are for 75°
F at 50% relative humidity. Lower temperatures and higher
relative humidity will increase these drying times while
higher temperatures and lower relative humidity will decrease
these drying times. Tack free - 5 hours; Dry hard - 8 hours;
Full cure - 48 hours.
6.12.7 Polyurethane Topcoat, High Solids (MIL-PRF-
85285, Type I).
6.12.7.1 Characteristics. This coating is a two-
component high solids, polyurethane coating formulated for
compliance with air quality regulations with a 420 g/1 (3.5
lbs/gal) VOC content.
6.12.7.2 Uses. Type I is intended for use on aerospace
weapons systems and other applications. Type II is intended
for use on ground support equipment and shall not be used on
aircraft due to its very low flexibility.
6.12.7.3 Advanced Performance Coating (APC), qualified
to MIL-PRF-85285, Type I, also known as Extended Life
Topcoat (ELT) is a chemically cured two component poly-
urethane topcoat formulated with fluorinated polyol resin to
provide a protective coating with exterior durability and
cleaning efficiencies superior to conventional MIL-PRF-
85285 polyurethane coating. APC, when used over MIL-
PRF-23377 or MIL-PRF-85582 epoxy primer, provides fade
TO 1-1-8
6-11