an improved urethane pre - polymer - based surface coating comprising a mineral filler the improvement comprising a thiophene compound and arylsulphorylisocyanate compound . a method of delaying or preventing the cross - linking or gelation of a urethane pre - polymer - based surface coating prepared with a mineral filler , comprises adding to of the formulation the surface coating a thiophene compound and an arylsulphonylisocyanate compound in amounts effective to prevent or delay the cross - linking or gelation of the surface coating .