A major breakthrough occurred with the discovery
of the basic diisocyanate polyaddition reaction
in 1937 [4], which was first applied to produce
polyurethane fibers and then to the development of
some elastomeric polyurethanes at DuPont and ICI
[5–7]. The work at DuPont focused on elastic fibers
and eventually led to the invention of elastic linear
copolyesters, prepared by melt-ester interchange
between two melt copolymerized polymers [8]. This
synthetic elastomer had higher strength than vulcanized
natural rubber and exhibited a rapid elastic
recovery. It was used to make fibers by extrusion
or spinning from solutions and can be considered
to be the first thermoplastic elastomer. The DuPont
patent dated 1954 [9] describes it as segmented
polyurethane fiber with excellent elastic properties.