lower than expected; this can be explained by the fact that a 0.83 a/
D ratio is high, which should increase interaction between HD
spheres.
To determine the order of magnitude of Stheo, the value of K (Eq.
(12)) has to be evaluated. Using ε0 ¼ 8.8$1012, εHD ~ 4ε0,
YSD ~ 106 Pa, E0 ¼ 106 V/m, and estimating the local effective field of
Eloc ¼ E0 (εr þ 2)/3, (see Ref. [9]) with the PUs permittivity εr ~ 8ε0,
we have K ~ 5.9$104, and as an example, the deformation of PU75
is then Stheo ~ 0.14% to be compare to the 1.7% measured. It is worthy
to notice that this value strongly depends on YSD which is difficult to
determine, and in the other hand the linear model is far from the
reality. However, the general tendency is correctly predicted, as
shown in Fig. 12.
This also suggests that the electrostriction properties of polyurethanes
polymers can be tuned by controlling the polymer
morphology, in terms of phase separation, HD diameter and
HDeHD distance. Among the further discussions to be conducted,
the effect of the distribution of inter-particles distance is an
important point, as it is clear than HD aggregates should lead to
lower efficiency than regularly repartition of HD. Within the aggregates,
almost no deformation should occur, and between the
aggregates, long distances should lead to weak deformations.
lower than expected; this can be explained by the fact that a 0.83 a/D ratio is high, which should increase interaction between HDspheres.To determine the order of magnitude of Stheo, the value of K (Eq.(12)) has to be evaluated. Using ε0 ¼ 8.8$1012, εHD ~ 4ε0,YSD ~ 106 Pa, E0 ¼ 106 V/m, and estimating the local effective field ofEloc ¼ E0 (εr þ 2)/3, (see Ref. [9]) with the PUs permittivity εr ~ 8ε0,we have K ~ 5.9$104, and as an example, the deformation of PU75is then Stheo ~ 0.14% to be compare to the 1.7% measured. It is worthyto notice that this value strongly depends on YSD which is difficult todetermine, and in the other hand the linear model is far from thereality. However, the general tendency is correctly predicted, asshown in Fig. 12.This also suggests that the electrostriction properties of polyurethanespolymers can be tuned by controlling the polymermorphology, in terms of phase separation, HD diameter andHDeHD distance. Among the further discussions to be conducted,the effect of the distribution of inter-particles distance is animportant point, as it is clear than HD aggregates should lead tolower efficiency than regularly repartition of HD. Within the aggregates,almost no deformation should occur, and between theaggregates, long distances should lead to weak deformations.
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