Design of voltage stabilizers for high breakdown strength materials

High breakdown strength material in the cable insulation layer is a key enabler for high voltage power transmission. In this work, we seek to design high-performance voltage stabilizers to be compounded into polyethylene to improve its breakdown strength. We hypothesize that electron affinity (EA) and HOMO-LUMO gap are two key factors that affect the performance of voltage stabilizers. To achieve larger EA and smaller HOMO-LUMO gap, we propose to use aromatic molecules decorated with electron acceptors and donors. A search of an internal chemical database narrows down to 529 molecules using structure, ClogP, and H-phrases (hazard statement) as criteria. The EA and HOMO-LUMO gap of these molecules are then calculated and experiments are carried out to measure the performance of 20 molecules. The performance improvement does not show a significant correlation with either EA or HOMO-LUMO gap. However, the best performers have an EA of 1.3-2.3 eV and HOMO-LUMO gap of 3.2-5.2 eV. The experimental study shows that adding side groups to voltage stabilizers will typically degrade their performance because side groups will generally increase the distance between the HOMO-LUMO orbitals and polyethylene backbone, and therefore decrease the electron/hole tunneling effectiveness. This image shows the scientific methods used in this study. A theoretical study is used to evaluate the effects of different functional groups on EA and HOMO-LUMO gap. Then high throughput calculation is performed on hundreds of voltage stabilizer candidates selected by a set of criteria, which is followed by experimental testing of dozens of molecules. Finally, examination of molecular orbitals and electronic properties helps achieve a fundamental understanding of the factors that affect performance.image