Effects of Methyl and Carbon-Carbon Double Bond in Anhydride Molecule on Dielectric Properties of Epoxy/Al2O3 Composite

Epoxy/Al2O3 composites are widely used as electrical insulating materials for high voltage electrical apparatuses. Organic acid anhydrides are important curing agents of electrical insulating epoxy composites. Functional groups and molecular structures of the acid anhydrides play significant roles in determining physical properties of the epoxy/Al2O3 composites. In this work, we investigate effects of the methyl and carbon-carbon double bond in organic acid anhydride molecule on the dielectric properties of epoxy/Al2O3 composite. We test the resistivities and AC breakdown voltages of epoxy/Al2O3 composites cured with five kinds of anhydrides, which are only different in the number and position of methyl and double bond. To explore the influence laws obtained from experimental results, we analyze the distributed energy level structures of five epoxy resin/anhydride oligomer molecules by carrying out a quantum chemical calculation, and the laws are used to predict the relative magnitude of molecular orbital energy levels of epoxy resin/phthalic anhydride oligomer molecule, which are consistent with the energy levels calculated. The double bond in acid anhydride molecule affects the LUMO and HOMO energy levels of an epoxy resin/anhydride polymer molecule, and the methyl in acid anhydride molecule affects the strengths of hydrogen bonds formed between the molecular chains and the silane coupling agents.

Automated summary

The study examines the effects of methyl and carbon-carbon double bond in organic acid anhydride molecules on the dielectric properties of epoxy/Al2O3 composite materials. It was found that these factors play significant roles in determining the physical properties and dielectric properties of the composite materials. Quantum chemical calculations were utilized to predict the relative magnitude of molecular orbital energy levels and explain the laws obtained from experimental results.