Abstract
In the case of research of ultrapure materials, manufacturing, analysis and containers are most important. It is impossible to produce pure materials without any one of these items. Polyethylene has been widely used for containers of ultrapure materials on a commercial basis. However, it is not so stable with strong acids. Teflon is the best one of many plastics protected from reagent as strong acids or alkalies and also against temperature. It is natural that Teflon, having these good properties, is considered to be good containers. However, the particles in Teflon being contained as metalic and oxide compounds of inorganic materials become a problem. Therefore, this investigation was carried out to confirm numbers, size, distribution and constituents of particles in plastics, especially in Teflon, with microscope and laser micro probe.
Particles in the Teflon bottles were from less than several microns to about 200 microns and many were less than 50 microns in diameter. Over about 5 microns particles which were detected with microscope were found in bottles about four or five times more than in pellets. Quantity of particles in plastics were 720 × 103/cm3 in Teflon, 9 × 102/cm3 in polyethylene and 7 × 102/cm3 in polypropylene bottles. As a result of this fact, it is known that the contamination was occurred remarkably during the process of molding from pellets to bottles. All particles distributed throughout and embdded in the Teflon bottles, in some cases the covering layer was very thin and the particles produced a rough inner surface in the bottles, and their state contaminates easily the storage materials. Particles in the Teflon bottles were analyzed and found that iron, titanium, magnesium, calcium and silicon as the major constituents, and nickel, chromium, copper and manganese as the minor constituents using the laser micro probe. Their colors were black, dark brown, white and others. The contents of iron, one of the typical element contained in the particles, were determined by 1-10 phenanthroline method and were 18 ppm in Teflon bottle and <0.5 ppm in original Teflon pellet.
