Flame retarded styrenic foams and foam precursors

Styrenic polymer foams, especially expanded and/or extruded styrenic polymer foams, are flame retarded by use of one or more flame retardant additives. These additives are i) a diether of tetrabromobisphenol-S, which ether groups do not contain bromine and wherein at least one of the ether groups is an allyl group; ii) a diether of tetrabromobisphenol-S, wherein at least one of the ether groups contains bromine; iii) a substituted benzene having a total of 6 substituents on the ring and wherein at least 3 of the substituents are bromine atoms and at least two of the substituents are C1-4 alkyl groups; iv) tribromoneopentyl alcohol; v) a tris(dibromoalkyl) benzenetricarboxylate in which each dibromoalkyl group contains, independently, 3 to 8 carbon atoms; vi) a brominated polybutadiene which is partially hydrogenated and/or aryl-terminated; vii) at least one brominated allyl ether of a novolac; viii) a brominated poly(1,3-cycloalkadiene); ix) a brominated poly(4-vinylphenol allyl ether); x) a brominated N,TSP-