(EN) The invention concerns a method for producing a thermoplastic molding material or element, said material or element containing nanometric inorganic particles. In molten state, the thermoplastic is mixed with the nanometric inorganic particles and with a solubilizing agent in a conveyor screw extruder, the pressures and temperatures being adjusted so that the plastic is in melt form and the solubilizing agent in supercritical state. The invention is characterized in that at the output of the extruder, the mixture passes through a slot with a passage less than 20 $g(m)m to penetrate into an expansion zone and the molten material, wherein are incorporated the nanometric inorganic particles, is evacuated, reduced into molding material after cooling or transferred into a molding tool to be molded. The invention also concerns the molding material and the molding elements obtained by this method, as well as the uses thereof.