Microwave transparent crosslinked polystyrene nanocomposites with enhanced high voltage resistance via 3D printing bulk polymerization method

Demanded by the application in ultrahigh pulsed power generator as vacuum insulator, the MgO-filled nanocomposites with enhanced high voltage resistance were developed on the basis of microwave transparent crosslinked polystyrene (CPS). Considering the severe thermal runaway problem, a proprietary fabrication method combing the in-situ preparation with 3D printing bulk polymerization technique was also innovated and bulk products with different filler loading were successfully fabricated. The microscope images suggested that the distribution of MgO in the products was uniform, whereat the excellent mechanical properties of CPS were well maintained. Furthermore, owing to the appropriate dielectric characteristics of MgO and tiny filler loading, the relative permittivity of the composites increased very slightly while the loss tangent below 20 GHz was less than 8×10−4, indicating the excellent transparency at the microwave band. Most importantly, the electrical breakdown strength was sharply improved from about 450 to over 600 kV/mm by only 0.1% MgO, as the barrier effect of electric double layer at the tremendous interface had effectively suppressed excessive charge injection and retarded electrical failure. Regarding the high voltage resistance obviously improved and the other properties well maintained, the CPS/MgO nanocomposites designed and developed in this work are applicable for the targeting application.