Keywords: hydrophobic coating, radome coating, rain attenuation,
rain fade, signal loss, super hydrophobic, improved satellite reception,
Fluorothane.
Note: See Fluorothane for hydrophobic
and super-hydrophobic aircraft, marine and ground radome coatings. See FluoroPel
for fluoropolymers and FluoroSyl for flluorosilanes.
International Electrochemical Commission Severity 2 Salt Fog Test On
Acrylic Painted SMC Panels And Reflectors Top-Coated With Fluorothane ME
& MS
Description: The International Electrochemical Commission severity
2 salt fog test cycle comprises indirectly exposing a substrate to atomized
5% salt solution for 4 hours at 15 to 35°C followed by a humidity storage
period of 20 to 22 hours at 40°C and 93% humidity.
Substrate: SMC panels and reflectors were painted with white acrylic
paint and allowed to cure. The panels was then spray painted with Fluorothane
ME or MS using gravity feed HVLP spray equipment. Dynamic pressure was 35
psi, feed was 2, and fan out was set to full width (1/3 turn). HVLP gun
was held 6 inches from substrate, moved at 6 inches per second, with 10%
overlap. Reflectors were spray painted using automated HVLP equipment with
similar settings. The coated substrate was allowed to cure at least 48 hours.
Reflectors were sawed into sections for this and other testing. Drop roll-off
angles at 20 locations on the panel were less than 2 degrees, corresponding
to receding contact angles of 140 to 170 degrees.
After curing, one corner of each substrate was cross-scored with a razor
blade through the coating and acrylic paint every half inch in a 4 inch
square pattern. A two inch band along an opposite edge was also abraded
by placing a 2 inch diameter one pound weight on a paper towel and dragging
it across the panel adjacent the edge. Drop roll-off angles at 5 locations
on the abraded area were still less than 2 degrees.
Salt Fog Test: Fluorothane ME or MS coated substrates were placed
in a 0.1 cubic meter chamber with a 3 inch diameter drain opening and three
1.5 inch vent openings in the cover panel. With the chamber held at 20°C,
ultrasonically atomized 5% salt solution was ported into the chamber oblique
to the test substrate. The chamber was filled with a dense white fog throughout
the four hour daily exposure period. During the subsequent daily 20 hour
periods of high heat and humidity, the panel was maintained at 40°C
heat with 95% relative humidity. This 24 hour cycle was repeated for 10
days. During weekends and holidiays, the panel was allowed to stand at ambient
lab temperature and humidity.
At the end of ten days for the MS coated reflector and twenty days for other
substrates, the test surfaces were rinsed with tap water for 5 minutes,
gently blown dry with compressed oil-free air, and then dried at 55°C
for one hour.
Evaluation: Visual inspection indicated no cracking, peeling, blistering
or delamination.. Drop roll-off angles taken immediately after drying were
all 2 degrees.
The substrates were then challenged with 10 inches of rain per hour for
24 hours. Roll off angles for all locations except the abraded area were
less than 2 degrees. The abraded area showed roll-off angles of 10 to 15
degrees, corresponding to contact angles of 120 to 130 degrees. The cross-cut
area showed no delamination or loss of contact angle.
Conclusion: Fluorothane ME and MS showed complete resistance to high
salt, high humidity environments that are expected for marine or coastal
installations.
Cytonix Corporation
8000 Virginia Manor Road
Beltsville, MD 20705
phone: (888) CYTONIX or (301) 470-6267
fax: (301) 470-6269 or email: emailbox@cytonix.com
