Shape Memory Polymer

1. Shape Memory Polymer
• Material :-
Shape memory polyurethane (SMPUs)
• Introduction:-
SMPUs can recover all the residual plastic deformation up to 400% through a
micro-Brownian movement triggered by heating them 10-20°C above their
glass transition temperatures (Tg).
• Shape memory effect :-
Shape memory PU(polyurethane) are composed of at three basic starting
materials, these are
(1) long chain polyether or polyester polyol,
(2) Di-isocyanate
(3) Glycol or diamine (chain extender).

2.  The shape memory effect of segmented polyurethane is due to the
network structure formed by hard and soft block. The hard blocks are
formed by the reaction of (2) Di-isocyanate with (3) low molecular weight
glycol, or Diamine (chain extender).
 On the other hand, soft segments are formed by (1) Polyol (oligomer).
 The hard blocks constitute about 30-50% by weight of the total polymer.
 The network structure can be easily deformed above glass transition
temperature (Tg) to give a temporary shape, the original shape can be
recover when the material heat above the glass transition temperature.
Fig :- Deformation of Shape Memory Polyurethane (SMPUs) Network Structure by Heat

3. Figure :- Temperature dependence of elasticity of SMPU
 At temperature above the glass transition temperature (Tg), the polymer achieves
a rubbery elastic state where it can be easily deformed without stress relaxation
by applying external forces over a time-frame t<<τ, where τ is a characteristic
relaxation time.
 After Cooling below Tg, the amorphous segment is ‘frozen’ in a glassy non-
crystalline state of high elastic modulus.
• The Mechanism of SMPU:-

4.  When the material is cooled below its Tg, the deformation is fixed and the
deformed shape remains stable. The pre deformation shape can be easily
recovered by reheating the material to a temperature higher than the Tg.
Figure :- Schematic drawing for the shape-recovery cycle of SMPU

5. Morphology, phase separation, thermal and mechanical
property differences of shape memory fibers prepared by
different spinning methods
In general, there are four different methods based on
 (i) dry, (ii) wet (iii) reaction, and (iv) melt spinning technologies for shape
memory polyurethane fibre preparation.
 In this paper, the mechanical properties, especially the shape memory
properties, of shape memory fibres (SMFs) prepared by the melt spinning
method and the wet spinning method were studied.
• Material:- The shape memory polyurethanes were synthesized using
poly(ε-caprolactone) diol-4000 (PCL) (Daicel Chemical Industrial) as the soft
segment and isophorone disocyanate (IPDI) (Aldrich Chemical Company) and
molecular extender 1,4-butanediol (BDO) (Acros Organics) as the hard
segment.

6. • Experiment:-
Melt Spinning Wet Spinning
 The shape memory polyurethane
monofilaments of 40 denier were spun
using a 20 mm single extruder with
highly pure nitrogen protection.
 To prepare SMFs by wet spinning,
the calculated polyurethane plates
were dissolved in DMF (N,N
dimethyllformamide) to make
polyurethane (PU) solution.
 The winding-up speed was 500 m/min,
with an overfeed speed of 10 m/min.
 The solution concentration was 45 wt%.
The SMFs were coagulated in an
aqueous precipitation bath.
 The temperatures at the first zone, second
zone, third zone, fourth zone, extruder
head, spinning pack, melt pipe and pump
were 190, 215, 218, 220, 222, 222, 222 and
222 ◦C, respectively. The laminar air
temperature was 22 ◦C. The extruder head
pressure was 5.00 MPa and the spin pack
pressure was 22.00 MPa. A spinneret with
a single 0.4 mm hole was used.
 The SMFs were coagulated in an
aqueous precipitation bath. The fibres
were then passed through two pairs of
rinsing rollers and hot rollers before
being wound on a friction winding-up
head at a speed of 20 m/min.
 The spinning experiments were conducted
three times under the same conditions
 The wet spinning experiments were also
conducted three times.

7. • Properties :-
1. Thermo-Mechanical properties by Differential scanning calorimeter (DSC) and
X-Ray Diffraction (XRD) analyses.
2. Elastic modulus by Dynamic mechanical analyses (DMA).
3. Mechanical property by Instron 4411.
• Conclusion:-
 It was observed that the melt-spun SMFs had higher tenacity, breaking
elongation and shape memory effect compared with those of wet-spun SMFs.
 The results indicate that the melt-spun SMFs have higher phase separation,
allowing for better soft-segment and hard segment crystallization, whereas
with wet spinning technology it is more difficult to produce well-organized soft
and hard segments.
 It is proposed that the melt spinning method is better than wet spinning for
obtaining high performance SMFs

8. Study on the Properties of Core Spun Yarn and Fabrics of
Shape Memory
 In this paper, shape memory textiles mean a fabric which is made of shape
memory polymer filaments and yarns.
• Yarn sample preparation and testing
Material and machine:-
o Shape memory fibre was spun by the wet spinning method at a switch
temperature of 58 °C.

9. Friction Spinning Ring Spinning
 Friction spun core yarn was spun
on a Dref-3 friction spinning
machine. Five carded cotton slivers
of 3.0 ktex linear density were
used as the sheaths.
 Ring spun core yarn was spun on an SKF
ring frame lab. The shape memory
fibres were sent to the front roller on
the ring spinning frame.
 One of these slivers and a shape
memory filament were used as the
core.
 The shape memory fibres were covered
and twisted with polyester staple fibres
in the spinning triangular space to form
core spun shape memory yarn, which
was then taken-up on a ring bobbin by a
spindle.

10. • Fabric Weaving:-
 Twill fabrics were woven using cotton yarn as the warp and shape memory core
yarn as the weft.
 Fabric 1 was woven with ring spun core yarn as the weft and fabric 2 with
friction core yarn as the warp.
• Testing:-
(a)Fiber & Yarn :- The tenacity of the shape memory fibre and core yarn were
tested on an Instron 4466 material testing machine in a standard atmosphere
environment. The testing velocity was 10 mm/min.
(b)Shape Memory Fabric :-The breaking strength and elongation of the shape
memory fabrics were tested on an Instron 4466 material testing machine
in a standard atmosphere environment using the ravelled strip test.

11. • Conclusion:-
1). Shape memory core spun yarn has as good shape memory effects as pure shape
memory fibre.
2). The fabrics with shape memory yarn as weft has better shape memory effects in
the filling-direction, but in the warp-direction without shape memory yarn also
shows some shape memory effects.
3). Ring spun core shape memory yarn has a higher breaking strength and looming
effects.
4). Fabrics with ring core shape memory yarn in the weft have better shape
memory effects than those of fabrics with friction shape memory yarn.