page_title: Roy J. Plunkett
section_title: Career
hierarchical_section_title: Roy J. Plunkett / Career
caption_attribution_description: LDEF (Flight), AO178&#160;: A High-Resolution Study of Ultra-heavy Cosmic-Ray Nuclei, Tray E10 The flight photograph of the Ultra Heavy Cosmic Ray Experiment (UHCRE) was taken while the LDEF was attached to the Orbiter's RMS arm prior to berthing in the Orbiter's cargo bay. The white paint dots on the center clamp blocks of the experiment trays left flange and lower flange appear to be slightly discolored. The UHCRE detectors were contained in 16 peripheral LDEF trays with at least one UHCRE tray located on each row of the LDEF except row 3, row 9 and row 12. Each tray contains three cylindrical aluminum pressure vessels with an integral aluminum support structure. Each cylinder is filled with an Eccofoam insert that houses 4 UHCRE detector stacks. Each stack consist of layers of Lexan polycarbonate sheets (approximately 70) interleaved with several thin sheets of lead. Forty-seven of the 48 pressure vessels were pressurized to 1.0 bar of a dry gas mixture (oxygen, nitrogen and helium) and sealed. One of the units was left unsealed in order to investigate the effects of the vacuum environment on the detector materials. Thermal control was accomplished by attaching an aluminized Kapton thermal cover on the tray bottom (the Kapton facing the LDEF interior), placing the aluminum cylinder support structure on thermal isolators and covering the experiment with a thin (5 mil) silvered TEFLON® thermal cover. The silvered TEFLON® cover was supported by an aluminum frame, an integral part of the experiment structure, and held in place by Velcro pads selectively located on the frame and on the back of the cover. The copper colored strip extending over the trays lower flange is a copper coated pressure sensitive tape used to provide an electrical ground between the experiments thermal cover and the LDEF structure. The UHCRE thermal covers surface appears to have changed from specular to opaque with numerous black dots of various sizes that appear to be impact craters. Many of the craters appear to have a black center encircled by a brown halo. Other circular discolorations also appear on the cover surface. The darker discolorations probably result from an impact that penetrates the 5 mil TEFLON® film and allows atomic oxygen to oxidize and/or erode the vapor deposited silver layer beneath. The cover is taut and the locations of Velcro attach pads are prominent. The ground strap appears to be intact with no visible damage but appears to be a deeper copper color.
context_page_description: Roy J. Plunkett was an American chemist. He discovered polytetrafluoroethylene, i.e. Teflon, in 1938.
context_section_description: In 1936 he was hired as a research chemist by E.I. du Pont de Nemours and Company at their Jackson Laboratory in Deepwater, New Jersey.
  The discovery of Teflon is best described in Plunkett's own words:
  On the morning of April 6, 1938, Jack Rebok, my assistant, selected one of the TFE cylinders that we had been using the previous day and set up the apparatus ready to go. When he opened the valve — to let the TFE gas flow under its own pressure from the cylinder — nothing happened...We were in a quandary. I couldn't think of anything else to do under the circumstances, so we unscrewed the valve from the cylinder. By this time it was pretty clear that there wasn't any gas left. I carefully tipped the cylinder upside down, and out came a whitish powder down onto the lab bench. We scraped around some with the wire inside the cylinder...to get some more of the powder. What I got out that way certainly didn't add up, so I knew there must be more, inside. Finally...we decided to cut open the cylinder. When we did, we found more of the powder packed onto the bottom and lower sides of the cylinder.
  Plunkett further relates that the cylinders of TFE being used contained about 1 kg each (2.2 pounds) which would be relatively small, lecture bottle sized cylinders, not large cylinders.
  The tetrafluoroethylene in the container had polymerized into polytetrafluoroethylene, a waxy solid with amazing properties such as resistance to corrosion, low surface friction, and high heat resistance. Plunkett related the story of this accidental discovery at the spring meeting of the American Chemical Society national meeting in the History of Chemistry section, April 1986 in New York City which was published in the Symposium Proceedings.
  He was the chief chemist involved in the production of tetraethyllead, a gasoline additive, at DuPont's Chambers Works from 1939 to 1952. After that he directed Freon production at DuPont before retiring in 1975.
caption: Teflon thermal cover showing impact craters, from NASA Ultra Heavy Cosmic Ray Experiment (UHCRE)
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