The invention relates to thermoplastic moulding materials containing A) 10–98 wt. % of at least one thermoplastic polyester, B) 1–30 wt. % of a flame resistant material combination made of 100 wt. % B), b1) 20 99 wt. % of a flame resistant material containing halogen b2) 1–80 wt. % of an antimonoxide, C) 0.01–5 wt. % of tartaric acid or tartrates or a mixture thereof, D) 0 is 5 wt.-% of at least one stabilisator containing phosphorous, E) 0–70 wt.-% of additional materials, whereby the sum of the wt % of the components A)–E) is 100%.