Abstract: A process for the manufacture of a closed cell, rigid, polymer foam from polymer foam-forming ingredients containing a filler which comprises:(a) dispersing the filler in at least a portion of the foam-forming ingredients to form a filled dispersion, a fluorochemical surfactant being incorporated in the foam-forming ingredients either before, during or after the dispersing operation to form a dispersion containing a filler and a fluorochemical surfactant,(b) mixing the dispersion formed in step (a) with any remaining foam-forming ingredient or ingredients, and(c) foaming and curing the resultant foam-forming composition.The fluorochemical surfactant improves the stability, flowability and mixing of the dispersion during the foam production.