Heat-Shrink Tubing

Paul Cook founded Raychem in 1957 to use radiation chemistry: electron beams that cross-link polyethylene chains so the plastic no longer melts, only softens. Such a material has a memory. Stretch it while hot, cool it stretched, and it keeps the new size until heated again - then it shrinks back tight onto whatever is inside. **US 3,086,242**, "Process and apparatus for producing materials having plastic memory", Cook and Muchmore, assigned to Raychem, filed 15. July 1960, granted 23. April 1963: tubing carried through a heated zone in a pressure vessel, expanded as it emerges, and cooled while expanded - "dimensionally heat-unstable tubing". **You measure the memory and use it**: free-shrink a sample and check where the plastic went, then insulate a crimped wire splice.