Zammarano that can respond to external stimulus by

Zammarano el al. 27
investigated the effects of nanoparticles such as clay and carbon nanofiber
(CNF) on HRR of PU foams with special attention given to melt dripping, the
result showed that CNFs form an entangled fiber network which eliminates melt
dripping and decreases the HRR.

Zhang et al. 28 developed
a method of coatings composed of chitosan/ the graphene oxide (GO) /alginate
deposited on the surface of FPU foam to improve flame-retardant and smoke
suppression properties of flexible polyurethane foam. The cone calorimeter test
results of the coated FPU foams showed a reduction in the peak heat release
rate (PHRR), peak smoke production rate (SPR), total smoke release (TSR), and
peak

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carbon monoxide (CO) production.

 

Shape memory appliance
 

Shape memory polymer (SMP) is a smart
material that can respond to external stimulus by changing its macroscopic
properties (such as shape and color) and then recover its original shape from
its temporary shape. 29 SMP can perform
important geometrical changes, when activated by several types of external
stimuli, and which can be applied to several emerging engineering fields, from
aerospace applications, to the development of biomedical devices. 30 The glass transition temperature Tg of polyurethane-series
SMP is a very important parameter, because the molecular motion differs above
and below Tg, allow to the mechanical properties differ markedly above and
below Tg. Then The shape fixity and shape recovery exist due to the difference in
these properties. 31 Tobushi
et al 31
studied the thermomechanical properties of polyurethane-shape memory polymer (SMP)
foams and the influence of shape-holding conditions on shape recovery.

Singhal et al. 32
developed ultra low density (0.015 g/cc) polyurethane shape memory foams.
Single Tg of 45–70°C was achieved. The
result showed that this SMPU bhave shape recovery of 97–98% over repeated
cycles, glassy storage modulus of 200–300 kPa and recovery stresses of 5–15 kPa,
and shape holding tests under constrained storage above the Tg showed stable
shape memory.

 Lee
et al. 33 Polyurethane flexible foam having
shape memory effects was synthesized from polyester polyol and
4,4_-diphenylmethane diisocyanate (MDI) following the quasi-prepolymer method
in the presence of water as the blowing agent. The results that the shape
fixability of the foam (82-95%) increases with the increasing amount of gelling
catalyst, and decreasing molecular weight of polyol. Density are from 0.32-0.30
g/cm3. The high shape fixability of the foam is based on the high foam density.
the shape recoverability was over 99% for all of the samples, due to the
networked structure of the materials.

Yu et al.34
investigated  the effect of moisture
absorption on glass transition temperature and the stress/strain behavior of
network polyurethane shape memory foam. The results demonstrated that water
absorption significantly decreased the Tg of the foam (from 67 to 5 ?C), tensile testing
exhibited 100% increases in failure strains and 500% decreases in failure
stresses.

Tey et al.35
studied the effects of long-term storage in compressed cold hibernated elastic
memory (CHEM) polyurethane foam. polyurethane foam with expansion rates of 380
and 1273% from the hibernated size against 1-N load can are achievable. Complete
strain recovery was achieved for a hibernation period of up to 2 months.