Civil Engineering Reference
In-Depth Information
(1)
1.4
(2)
1.2
1.0
CP23
0.8
0.6
0.4
CP12
0.2
CP06
SMP
0.0
0
5
10
Time (min)
15
20
25
Figure 3.5
Recovery process of the composites under thermal and water stimulus. (1) Stress-release
recovery; (2) thermal induced recovery in the dry-state; (3) thermal and water-induced recovery by
immersing into hot water (65°C). Reproduced with permission from[41].
Figure 3.6
Photographic demonstration of the shape recovery of the composite prepared with 12 wt%
cellulose nanowhiskers: (a) temporary shape i xed in the dry and cool state (elongation of around 300%);
(b) temporary shape at er stimulation with heat; (c) temporary shape at er stimulation with cool water;
(d) original shape at er stimulation with hot water (68ºC). From Luo
et al.
[42] , with permission.
h e same research group Luo
et al.
[42] demonstrated in a later work that these
composites can of er up to i ve paths of shape recovery with choices of dual, triple, and
quadruple shapes using only one-step programming. Photographs recording the qua-
druple shape recovery of the composite using water and heat stimulations are presented
in Figure 3.6. h e authors indicated that the i rst thermo-sensitive switch was due to
the transitions of the PCL-based polyurethane. In the second, the naked water-sensitive
switched due to the percolation of the cellulose network distributed in the polyure-
thane's amorphous region where the hydrogen bonding was disrupted by cool water.; In
the third one, shielded water-sensitive switched due to the percolated cellulose network
embedded in the PCL crystals where the hydrogen bonding was only disrupted at er
PCL crystals were melted in hot water. h e triple-switch structure of the composite is
schematically illustrated in Figure 3.7. h is composite, with a high level of adaptability,
was proposed for developing novel functional polymeric composites.
