The Shuttle Ice Liberation Coating (SILC) has been developed to reduce the adhesion of ice to surfaces on the space shuttle. SILC, when coated on a surface (foam, metal, epoxy primer, polymer surfaces), will reduce the adhesion of ice by as much as 90 percent as compared to the corresponding uncoated surface. This innovation is a durable coating that can withstand several cycles of ice growth and removal without loss of anti-adhesion properties.
SILC is made of a binder composed of varying weight percents of siloxane(s), ethyl alcohol, ethyl sulfate, isopropyl alcohol, and of fine-particle polytetrafluoroethylene (PTFE). The combination of these components produces a coating with significantly improved weathering characteristics over the siloxane system alone.
In some cases, the coating will delay ice formation and can reduce the amount of ice formed. SILC is not an ice prevention coating, but the very high water contact angle (greater than 140º) causes water to readily run off the surface. This coating was designed for use at temperatures near –170 ºF (–112 ºC). Ice adhesion tests performed at temperatures from –170 to 20 °F (–112 to –7 ºC) show that SILC is a very effective ice release coating.
SILC can be left as applied (opaque) or buffed off until the surface appears clear. Energy dispersive spectroscopy (EDS) and x-ray photoelectron spectroscopy (XPS) data show that the coating is still present after buffing to transparency. This means SILC can be used to prevent ice adhesion even when coating windows or other objects, or items that require transmission of optical light. Car windshields are kept cleaner and SILC effectively mitigates rain and snow under driving conditions.
This work was done by Trent Smith of Kennedy Space Center; Michael Prince, Charles DeWeese and Leslie Curtis of Marshall Space Flight Center; and Erik Weiser and Roberto Cano of Langley Research Center. For more information, contact the Kennedy Space Center Innovative Partnership Program Office at (321) 861-7158. KSC-13100/1.