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.
The GM 9540P Salt Fog Test on Fluorothane ME and M1
Description The GM 9540P accelerated test protocol was selected because
of the amount of published data relative to the test and also because it
was already widely used in many industries. The test applies a 1.25% salt
solution as a mist in four consecutive intervals over a 4.5 hr period followed
by eight hours in high humidity @ 49 ± 2C and an eight-hour dryoff
at 60 ±2C. A 24-hr test period constitutes one test cycle.
Substrate: Four 6 by 6 inch SMC panels of were painted with white
alkyd paint and allowed to cure for 72 hours. Two painted panels each were
then spray painted with Fluorothane ME and Fluorothane M1 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. Coated substrates
were allowed to cure 48 hours. Cured panels had drop roll-off angles of
less than 2 degrees, corresponding to receding contact angles of 140 to
170 degrees.
Salt Fog Exposure: Panels were exposed to 22 twenty four hour cycles
of the GM9540P protocol, comprising 4.5 hours of indirect exposure to atomized
1.25% salt solution, followed by 8 hours at 50°C and 95% relative humidity,
and thereafter 8 hours at 60°C with low humidity. Panels were stored
under ambient conditons over weekends and vacations.
Evaluation: Panels were rinsed with cool tap water for five minutes,
blown dry with an air gun, and then dried at 60°C for 2 hours. Visual
inspection indicated no cracking, peeling, blistering or delamination on
any of the panels. Average drop roll-off angles take over nine loacations
on each panel were 2 degrees for Fluorothane ME and 2.7 degrees for Fluorothane
M1. Fluorothane M1 had one 4 mm diameter spot (out of 18) where the roll-off
angle was 15 degrees, and microscopically there was evidence of erosion
at that location.
Conclusion: Both Fluorothane ME and Fluorothane M1 showed complete
or substantial 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
