2 g and the refractive index was measured to be 1 53 hereinafter ytterbium fluoride is referenced as a radiopaque agent powder the radiopaque agent powder is then blended with a plastic material wherein a preferred composition comprises a fill ratio of about 30 parts nanoparticles of ytterbium fluoride about 70 parts of plastic material and about 0 1 parts of plasticizer dispersant additives a resin of pvc is the preferred suitable plastic material preferably the composition contains about one to about 50 weight of the plastic material the radiopaque agent powder selected for its uniform particle shape and controlled particle size distribution as described above is subsequently introduced into a vat containing the molten plastic material thus the solid powder molten polymer and additives are homogenized as they are agitated and subsequently introduced into the melt stream via the extrusion process the resulting polymer nanoparticle mixtures were then tested for radiopacity and appearance as to translucency the results being as follows as with example 1 other suitable plastic materials include silicones polypropylene polyester polyolefin fluoropolymers such as polytetrafluoroethylene ptfe polyethyl urethanes polyether block amides peba polyethylene terephthalate pet and blends or mixtures thereof the following three tables set forth the measured radiopacity of three different materials polypropylene table 1 silicone table 2 and pebex u00ae table 3 using various amounts of the noted ytterbium material fillers pebex u00ae is a tradename for polyether block amides peba manufactured by arkema inc of philadelphia pa it is a plasticizer free thermoplastic elastomer belonging to the engineering polymer family these amides are easy to process by.