| abstract |
A polyalkylene terephthalate polymer, such as polyethylene terephthalate, polybutylene terephthalate, blends or copolymers thereof, and analogous polyester-type engineering thermoplastics, with which has been blended a flame retardant amount of brominated styrenic polymer, such as brominated polystyrene, that, prior to blending, is characterized by: a) containing less than 700 ppm C1 and having a TGA temperature for 1 % weight loss of 340 °C or higher; and/or b) having an actual Mw which is within 20 %, and preferably within 10 %, of its calculated theoretical Mw, the theoretical Mw being based upon the actual bromine content of the brominated styrenic polymer and the Mw of the styrenic polymer reactant used to produce the brominated styrenic polymer; and/or c) being essentially free of each of the following impurities: 1) ethylene dichloride; 2) bromodichloroethane; 3) dibromochloroethane; 4) dibromodichloroethane; and 5) tribromochloroethane. These compositions most preferably also further comprise a reinforcing amount of glass fiber and/or a flame retardant synergist dispersed therein. It is now possible to provide polyalkylene terephthalate compositions that have a UL-94 rating of V-O using both 1/16-inch test specimens and 1/32-inch test specimens, and that have superior electrical resistance characteristics as reflected by a higher comparative tracking index and greater melt stability as determined by capillary rheometry. |