Abstract: Flame-retardant thermoplastic composition including a styrene polymer containing thoroughly incorporated therein an effective quantity of a synergetic mixture composed of a chlorinated hydrocarbon compound containing at least 40% by weight of combined chlorine, an inorganic compound containing oxygen of a metal belonging to group III or IV of the periodic table, and polytetrafluoroethylene having a particle size which is less than 20 microns.

Abstract: Moulding thermoplastic compositions, endowed with improved mould release characteristics, comprising:A) an impact resistant vinyl aromatic copolymer consisting of an ethylenically unsaturated nitrile, a vinyl aromatic monomer and a rubber;B) an engineering polymer; andC) an effective amount of a release agent constituted by a synergistic mixture of an ester of a C.sub.16 -C.sub.18 acid with glycerol and an ester of a saturated aliphatic C.sub.10 -C.sub.20 acid with a C.sub.4 -C.sub.6 aliphatic alcohol.The physical-mechanical properties of the compositions at high moulding temperatures can be improved by addition of an effective amount of a bis(alkyl-phenyl)pentaerythritol diphosphite.The compositions can, furthermore, contain in addition a grafted polymer consisting of an elastomeric core having a Tg lower than 10.degree. C. and containing vinyl monomer chains grafted thereon.