in 1969, bob gore was researching a process for stretching extruded ptfe into pipe thread tape when he discovered that the polymer could be "expanded" into a porous form of ptfe, characterized by extremely high strength and porosity. he and others had attempted to stretch rods of ptfe by about 10%. his discovery of the right conditions for stretching ptfe was a happy accident, born partly of frustration. instead of slowly stretching the heated material, he applied a sudden, accelerating yank. the solid ptfe unexpectedly stretched about 800%, forming a microporous structure that was about 70% air.