A process for the preparation of aziridine-functional polycarbodiimides comprising the steps of: i) the reaction of polyisocyanates or a mixture of mono- and polyisocyanates at 80 - 200 °C in the presence of 0.02 - 5 weight percentage of a carbodiimide catalyst, in which an isocyanate functional polycarbodiimide, optionally in admixture with a polycarbodiimide, is formed with a mean value of 1 - 10 carbodiimide functions; and ii) terminating and/or chain extending the isocyanate functional polycarbodiimide chain, during or after the formation of the polycarbodiimide chain, by the addition of 0.05 to 0.95 equivalent, regarding to the isocyanate functions that are not consumed in the formation of the polycarbodiimide chain, with a first compound containing a hydrophilic group and one or multiple amine and/or hydroxyl functions, together with, prior to, or followed by reacting the remaining isocyanate functions with one or multiple second compounds containing one or multiple amine and/or hydroxyl functions, in which 0 to 60 weight% of an organic solvent and/or 0 to 50 weight% of a plasticizer, and/or 0 to 30 weight% of surface active component is added during, before or after the carbodiimide forming reaction and/or the terminating reaction and/or the chain extending reaction, wherein at least one of the second compounds containing one or more amine and/or hydroxyl functions also contains one or multiple aziridine functional groups as additional functional group and is an ester of one or more 1-Aziridinealkanoic acid moieties or derivatives thereof. i) the reaction of polyisocyanates or a mixture of mono- and polyisocyanates at 80 - 200 °C in the presence of 0.02 - 5 weight percentage of a carbodiimide catalyst, in which an isocyanate functional polycarbodiimide, optionally in admixture with a polycarbodiimide, is formed with a mean value of 1 - 10 carbodiimide functions; and ii) terminating and/or chain extending the isocyanate functional polycarbodiimide chain, during or after the formation of the polycarbodiimide chain, by the addition of 0.05 to 0.95 equivalent, regarding to the isocyanate functions that are not consumed in the formation of the polycarbodiimide chain, with a first compound containing a hydrophilic group and one or multiple amine and/or hydroxyl functions, together with, prior to, or followed by reacting the remaining isocyanate functions with one or multiple second compounds containing one or multiple amine and/or hydroxyl functions, in which 0 to 60 weight% of an organic solvent and/or 0 to 50 weight% of a plasticizer, and/or 0 to 30 weight% of surface active component is added during, before or after the carbodiimide forming reaction and/or the terminating reaction and/or the chain extending reaction, wherein at least one of the second compounds containing one or more amine and/or hydroxyl functions also contains one or multiple aziridine functional groups as additional functional group and is an ester of one or more 1-Aziridinealkanoic acid moieties or derivatives thereof. in which 0 to 60 weight% of an organic solvent and/or 0 to 50 weight% of a plasticizer, and/or 0 to 30 weight% of surface active component is added during, before or after the carbodiimide forming reaction and/or the terminating reaction and/or the chain extending reaction, wherein at least one of the second compounds containing one or more amine and/or hydroxyl functions also contains one or multiple aziridine functional groups as additional functional group and is an ester of one or more 1-Aziridinealkanoic acid moieties or derivatives thereof.