High breakdown strength polymer nanocomposites based on the synergy of nanofiller orientation and crystal orientation for insulation and dielectric applications

Emerging energy and insulation applications require dielectric materials that can operate at high electric fields and meanwhile possess low leakage currents. For dielectric polymer nanocomposites, beyond filler dispersion, tailoring hierarchical structures offers a promising, yet largely untapped, approach to reach this goal. Here, we demonstrate that the controlled arrangement of pseudo-2D nanofillers and polymer crystals in polyethylene/montmorillonite nanocomposites can be used as an effective approach to achieve nontrivial highly enhanced dielectric performances, far beyond what is feasible with conventional (macroscopic, isotropic) composites. In particular, it is shown that aligned nanofillers can increase the breakdown strength, while, at the same time, reducing the leakage current, in these dielectric nanostructured composites. The orientation of the nanosized pseudo-2D fillers increases the path tortuosity for charge transport, acting as an effective geometric barrier, in the same way and in addition to the oriented polymer crystals of the polymer matrix. Thus, incorporation of aligned nanoplatelet fillers provides an independent and complementary increase to breakdown strength, in excess of any improvements due to the crystal orientation. In this manner, a substantially improved breakdown strength can be realized in the nanostructured composite, with the aligned fillers and aligned polymer crystals acting as a macroscopic barrier established across the sample.