**4. Conclusions**

A brief introduction of the physical properties of PI films and their derived nanoparticles was described in this chapter. The preparation of PI nanocomposite is a complex process with many variables involved. Several methods were probed before an optimal synthesis process was found. A detailed synthesis process optimization of multilayer PI nanocomposite films is described in this chapter to understand all variables, which can influence the dielectric properties of the final product. The polyimide/nanocomposite multilayer 3D model based on actual boundary conditions from SEM images of synthesized samples is also constructed and simulated in COMSOL multiphysics software. Effect of nanoparticle agglomeration in microstructures, with the impact of nanoparticle dispersion on the electric field enhancement, is explicitly described in this model. The dielectric properties such as space charge using thermal step method (TSM) technique were also measured to compare simulation results. Our results demonstrate that the chances of nanoparticle agglomeration are reduced by using a thin layer of PI/nanocomposite on PI film instead of using one single layer of PI/nanocomposite film. In consequence, less space charge and low electrical fields are observed in multilayer films. Our methods will help to reliably predict the dielectric strength of polymer/ nanocomposite insulating materials. Additionally, the new synthesized multilayer PI/nanocomposite insulating material will ensure reliable operation for electric motors and increase its lifespan.
