Effect of Heat Treatment on Power Frequency Breakdown Voltage and Dielectric Properties of Polylactic Acid

With the rapid development of green power grid, polylactic acid (PLA), a biodegradable material, is the basis and forerunner of high and new technology, and has a broad application prospect in power system. In this paper, the effects of thermal aging at 60°C on the electrical and dielectric properties of polylactic acid (PLA) were studied based on the application scenarios of PLA. The polylactic acid after drying was placed in a constant temperature aging chamber, and its macroscopic properties were measured by sampling every other day. It was found that the power strobe flashover voltage of PLA showed a significant rising trend with the increase of heat treatment time, and the breakdown voltage increased by 48% after heat treatment. The relative dielectric constant first increased and then decreased, and the dielectric loss did not change significantly. In this paper, molecular dynamics simulation analysis showed that the -OH and C=C functional groups in the molecular structure of PLA decreased after heat treatment, while C=O increased significantly. It is also found that the increase of the lowest-occupied molecular orbital-highest occupied molecular orbital (LUMO-HOMO) horizontal gap from 12.93 eV to 13.80 eV leads to a significant increase in the breakdown voltage of PLA materials. This study will provide theoretical basis for the application of PLA in complex power grid conditions.