Polycarbonate compositions including carbon nanotubes (CNTs) as microwave absorbers in automotive radar sensor applications

A thermoplastic composition comprising:

• (a) a polycarbonate resin;
• (b) a poly (carbonate-siloxane) copolymer having a siloxane content of at least about 5 wt %;
• and
• (c) from about 0.15 wt % to about 4.5 wt % of a carbon nanotube filler, wherein
• the carbon nanotubes have an average diameter of from about 8-12 nanometers (nm), a length of about 5 micron (μm) or less, a surface area of about 220 square meters per gram (m2/gr) or higher, and a volume resistivity lower than about 10−2 Ohm·centimeters (Ohm·cm),
• the composition has a volume electrical resistivity of at least about 1.0E+06 Ohm·centimeters (Ohm·cm) as determined in accordance with ASTM D257,
• a molded sample of the composition has a percent absorbed power measured in Transmission mode of at least about 60% when observed according to a Free Space method at frequencies from about 75 GHz to 110 GHz, and
• the combined weight percent value of all components does not exceed 100 wt %, and all weight percent values are based on the total weight of the composition.