You say "the gas had reacted with the cylinder, which was made of tetrafluoroethylene". Tetrafluoroethylene is a gas, not the sort of substance cylinders are made of. As I heard the story from Professor Eric Banks of Umist, an authority on organofluorine chemistry, Plunkett was surprised to find that a cylinder which should have contained tetrafluoroethylene was registering on the pressure gauge as being empty. He then took the brave step of cutting the cylinder open (a highly risky thing to do which would breach the safety regulations in any modern chemistry laboratory), and found that the tetrafluoroethylene had polymerised to give the greasy white solid polytetrafluoroethylene, which became known as PTFE or Teflon.
D. Roberts, FRSC