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.
Rapid Heat Cycle Test On Acrylic Painted SMC Panels And Reflectors Coated
With Fluorothane ME & MS
Description: Exceeding the International Electrochemical Commission
(IEC) 68-2-2 protocol in severity, the current test rapidly and repeatedly
cycles a coated test panel between -5°F and 160°F. The average
rate of temperature change, both positive and negative, was over 10 degrees
per minute.
Substrate: SMC panels and SMC reflectors were painted with white
acrylic paint and allowed to cure. The panels were 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 coated with ME or MS using automated HVLP equipment
with similar settings. The coated substrate was allowed to cure 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 alkyd paint every half inch in a 4 inch square
pattern. A two inch band along an opposite edge was also abraided 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.
Temperature Cycling: A thermocouple was attached to a substrate,
and it was suspended in a freezer at -10°F until it reached -5°F.
The substrate was then immediately suspended in a 165°F oven until
it reached 160°F. On reaching 160°F, the substrate was returned
to the freezer. This process was repeated ten times for each substrate.
After the final high temperature cycle, the substrate was allowed to come
to room temperature.
Evaluation: Roll off angles for 20 locations taken immediately were
less than 2 degrees. The panels and reflector sections 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 were uncompromised by rapid temperature
cycling and can be expected to perform well in both cold and hot environments.
The results of abrasion were no better or worse than those observed using
fresh panels that have not been challenged by adverse environmental conditions.
Scored areas and unabraded areas showed no evidence of erosion or water
penetration.
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
