In various aspects, the invention relates to blended thermoplastic polymer compositions (e.g., polycarbonate or polycarbonate-polysiloxane copolymer compositions) comprising recycled acrylonitrile-butadiene-styrene (ABS) polymer or recycled polystyrene polymer which contain at least one impurity and an acid melt flow stabilizer. The presence of the acid melt flow stabilizer improves the thermal stability of the polymer blend. In various further aspects, blended compositions further comprise a flame retardant. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present invention.