Aqueous fluoropolymer formulations containing in finely divided form from 15 to 75% by weight of a fluoropolymer which preferably has at least 40% by weight of tetrafluoroethylene units, from 0.5 to 10% by weight of an organic compound which has at least two, preferably 2-4, isocyanate groups and, optionally, up to 20% by weight of auxiliary or additive substances are prepared and used for coating yarn, in particular sewing yarn, and textile sheet materials.