The apparent electrical breakdown field, defined by the voltage applied divided by the thickness
at the maximum strain, increases monotonically, from 114 V μm-1 in C0-P0 to 236 V μm-1 in
C5-P0. The increase could be explained as the synergic effect of the suppression of EMI
(explained below) and improvement of the intrinsic breakdown field. On the other hand, the
maximum area strain sA shows a non-linear decrease along with increased crosslink density,
from 318% in C0-P0, 125% in C2-P0, to 70% in C3-P0, a minimum of 56% in C4-P0, and then
increasing to 89% in C5-P0. As seen in Figure 2-6, EMI is responsible for the large strains in the
lightly crosslinked elastomers (C0-P0).