US Patent 7232854 Polycarbonate compositions with thin-wall flame retardance

Polycarbonate compositions containing a specific combination of additives achieve desirable flame retardance characteristics when used in thin wall polycarbonate articles. These compositions contain a polycarbonate/siloxane component, containing a polycarbonate siloxane copolymer, or a mixture of a polycarbonate siloxane copolymer and polycarbonate resin; a mineral filler; and a flame retardant. The composition contains at least 50% by weight of polycarbonate when the polycarbonate of the polycarbonate siloxane copolymer and any polycarbonate resin (linear or branched) are considered together; and the polycarbonate siloxane copolymer and the mineral filler are present in amounts effective to achieve a flex modulus of 29,000 kg/cm3 or greater, for example 30,000 kg/cm3 or greater, good flex-fold strength and good impact strength, for example a room temperature Notched Izod Impact Strength of 25 kgf-cm/cm or greater. The composition also includes a flame retardant to enable the composition to obtain a UL94 rating of V0 at test thicknesses of 1.2 mm.