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 (–22°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 specific 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.
