TM55-1500-345-23
angle of impact. Angular impact determinations
and application procedures are
must be based on the position of the part when in
flammable and toxic in sufficient con
a normal inflight attitude.
centration, standard precautions such
as fire prevention and adequate ventila-
tion shall be exercised.
NOTE
Plastic parts to be coated with erosion resistant
Only the amount of material to be used
coatings should be processed in a sheltered area
within the following 8 hours should be
free from dust, and protected from weather
accelerated at one time. Material that
conditions. Best results are obtained if the coat-
has been mixed and allowed to stand
ings are applied at relative humidities below 60
beyond this period of time should be
percent.
discarded. Do not attempt to thin any
coating material which has gelled
a. Application of Coating System, Military
beyond brushable use. Keep containers
Specification MIL-C-83231.
tightly covered when not in use.
(1) Mixing. Components of classes A and
6-32. PREPARATION OF SURFACE.
B, types I and II coatings shall be individually
mixed in accordance with the manufacturer's
instructions. The resulting individual mixtures
shall be smooth, homogeneous materials free
METHYL ETHYL KETONE
from lumps, gelling. seeding, separation or other
Keep away from heat and open flame,
objectionable characteristics.
Keep container closed.
Use with adequate ventilation.
(2) Pot Life. Classes A and B coatings
Avoid prolonged breathing of vapors.
shall have a minimum pot life of 4 hours at stand-
Avoid prolonged or repeated contact
ard conditions. At the end of the 4 hour period, the
with skin.
coatings shall show no signs of lumping, seeding.
separation or an increase in viscosity of more
Failure to observe these precautions con result in
than 20 percent from the initial viscosity
serious injury or systemic poisoning of personnel.
(3) The class A and B coatings shall be
a. Repair surfaces with pits, scars, scratches,
applied in accordance with the manufacturer's
or other minor defects in accordance with TM 55-
instructions to a total dry film thickness of 12 to
1500-204-25/1. It has been found that coatings are
14 mils. The total application time, including prim-
more satisfactory if the surface to receive the
ing and intervals between coatings shall not
coating is smooth but not glossy.
exceed 8 hours. The tack free drying time for class
A coatings shall not exceed 4 hours after applica-
b. Remove surface gloss with a fine grade of
tion of the final coat. The tack free drying time for
emery or sandpaper, No 240 grit, after sanding
class B coatings shall not exceed 10 hours after
slightly with a coarser grade of abrasive so as to
application of the final coat.
finely and uniformly scratch the surface. Remove
sanding dust with a clean, lint-free cloth damp-
(4) The rate-of-cure of the class A and B
ened with methylethylketone, Federal Specifica-
coatings shall have a maximum set-to-touch or
tion TT-M-261, or thinner solvent used with the
recoat time of one hour. For class B materials, the
coating. Assure that surface is completely dry
manufacturer shall furnish instructions for cata-
before coating application.
lyzing or accelerating the polyurethane prepoly-
mer materials for a temperature range from 10C
6-33. APPLICATION OF PRIMER AND
to 35C (65F to 95F) and a relative humidity
COATING.
range from 40 percent to 75 percent.
(5) Class A coatings shall be fully cured
within 5 days and shall be free of pinholes, cracks,
Since materials used in coating removal
6-21
