The invention describes a composition comprising a) an organic material which is susceptible to oxidative, thermal or light-induced degradation, and b) at least one melt additive of a compound of the formula I R1(I)R3XR2 wherein the general symbols are as defined in claim 1. The compounds of the formula I are useful as reducers of surface energy for organic materials, for example, for increasing the oil and water repellency of organic materials. ##STR00001##