PTFE Sheet: Compact-Extruded Films, Sintered, Laid at 45° and Fused (MacFarland, Hills-McCanna, US 3,130,954)

Thick PTFE was cut from a sintered billet with a knife, and the skived sheet tore along the knife marks. MacFarland built his sheet up instead, from thin extruded films laid crosswise and fused together, for the liner of a valve diaphragm. Result: a dense PTFE sheet, about 7,000 psi tensile and 450 % elongation, much the same in every direction. Source: MacFarland, US 3,130,954 (Hills-McCanna, 1964). Not given: furnace temperature, mill pressure. Picture drawn by Youblob.