PTFE Thread Seal Tape: Paste-Extruded, Calendered, Never Sintered

The white tape wound on pipe threads is PTFE that has never been melted. Fine PTFE powder is mixed with a lubricant, pressed into a slug, squeezed through a slit die by a ram, rolled thin between two rolls, and dried. Kept below the sintering heat (about 350 °C) it stays soft and conforms to the thread (process: US 5,415,939, 1995). The targets and tests are those of the Indian standard IS 14643 (from BS 4375): no fillers, at most 0.1 % lubricant left, usually 12 mm wide and 0.075 mm thick. The lubricant (naphtha) and the slitter are ours. The picture: Fig. 1a of the patent.