Shape memory polymers

Question 1

In SMP the shape shifting and recovery are achieved through what?

Answer 1

a
polymeric segmental phase transition.

Question 2

What do the two phases inside polymers allow for?

Answer 2

one allowing for shape fixity (hard
segment/net points/frozen portion) and the other allowing for
reversibility or recovery (soft segments)

Question 3

Polymer shape memory occurs due to what?

Answer 3

glass transition (the
temperature at which the phase changes from a rigid to a flexible,
soft phase) or the melting transition of a hard segment to a soft
segment.

Question 4

Entropy elasticity, a property of SMPs that releases polymeric chains
from their strained configuration (the temporary trained shape) to a
less complex configuration (the original shape as memorized), acts as a what?

Answer 4

an impetus for shape memory realization.

Question 5

Three-dimensional molecular network formed by cross-linked
polymer net points, provides?

Answer 5

stability in both the original and
recovered shapes

Question 6

The cross-linking domain can be either physical, which is achieved by forming crystalline or glassy phases or what?

Answer 6

; or chemical,
where the individual polymer chains are linked by covalent bonds

Question 7

what are the two mechanisms?

Answer 7

Dual-component mechanism (DCM) and Dual-state mechanism (DSM), Partial-transition mechanism (PTM):

Question 8

how does the duel state mechanism work?

Answer 8

The molecular chains are the reversible
phase and the nodes of macromolecule segments (analogous to
matrices in composites) attributed to physical or chemical cross-links
are the permanent phase.

Question 9

How does the dual component mechanism work?

Answer 9

One component is elastic and
the other is able to switch stiffness, depending on the stimuli.

Question 10

how does the Partial-transition mechanism (PTM) work?

Answer 10

Instead of a complete transition,
heating may stop at a temperature within the transition range. As
such, when deformed, the unsoftened portion may serve as the
elastic component to store elastic energy, while the softened portion
may behave as the transition component.

Question 11

Advantages of SMPs?

Answer 11

• Density is lower.
• Not only the cost of raw material but also the cost in fabrication and
  processing is lower.
• Recoverable strain is normally an order higher than that in SMAs
• It is easy to tailor the thermo-mechanical properties of SMPs by
  means of, for instance blending with different types of fillers or
  varying the compositions
• Shape recovery temperature range can be easily altered within a wide
  range and even gradient