A polymer engineered with shape
memory characteristics provides a unique set of material qualities
and capabilities that enhance the traits inherent in the polymer
system itself. SMP changes between rigid and elastic states
by way of thermal stimuli. The change takes place at what
is referred to as the glass transition temperature (Tg). SMP
can be formulated with a Tg that matches an application need.
Current SMP systems have been demonstrated with Tgs from –30
°C to 260 °C (–20 °F to 500 °F).
Above its transition temperature, which
can be custom-engineered, SMP goes from a rigid, plastic state
to a flexible, elastic state. When cooled below that temperature,
it becomes rigid again, with high specific strength. The SMP
can be manipulated and cooled into a variety of new shapes;
when heated above its transition temperature, it will return
to its "memorized" shape.
Shape memory polymers are characterized
by triggering segments that have a glass transition temperature
(Tg). At a temperature above Tg, the material can be easily
deformed. The deformed shape will be maintained when the material
is cooled below the Tg. The material will "remember"
or return to its original shape when it is heated to a temperature
above the Tg again. The material should be manipulated in
its fully elastic state and not in the temperature transition
range.
