Significantly improved high-temperature capacitive performance in polypropylene based on molecular semiconductor grafting

The high-temperature dielectric properties and energy storage performance of capacitive materials are of great significance for the sustainable development of new energy-related fields. However, the most widely used commercial capacitor dielectric biaxially oriented polypropylene (BOPP) films fail to satisfy the requirements of continuous operation above 105 degrees C at high electric fields. Here we demonstrate a molecular semiconductor-grafted polypropylene (PP) composite that possesses substantially enhanced dielectric and capacitive performance up to 120 degrees C by virtue of the modulated carrier transport behavior. The organic molecular semiconductor [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is chemically grafted onto PP chains (PCBM-g-PP) to achieve strong interaction and decent compatibility between the PCBM and the polymer matrix. Based on computational simulation and experimental verification, it is confirmed that the grafted molecular semiconductor introduces deep traps to inhibit the migration of high-energy charge carriers excited by heat. In the meantime, the grafting also helps to intensify the regulation effect by exerting positive influences on the microstructure of the polymer. The PCBM-g-PP/PP composite films possess reduced leakage current and dielectric loss, as well as suppressed electric field distortion and elevated breakdown strength. At 120 degrees C, the energy storage density of the composite with an efficiency above 90% reaches 1.59 J/cm3, which is 683.62% that of the original PP film. The reported molecular semiconductor-grafting strategy is expected to promote the capacitive performance of poly-propylene under hash-temperature conditions, facilitating the development of lightweight and compact-size dielectric capacitors. (c) 2023 Elsevier Ltd. All rights reserved.

Automated summary

This study demonstrates the improved dielectric and capacitive performance of a polypropylene composite by grafting a molecular semiconductor onto polypropylene chains. The grafted molecular semiconductor introduces deep traps to inhibit the migration of high-energy charge carriers and enhances the regulation effect by positively influencing the microstructure of the polymer. The composite exhibits reduced leakage current, dielectric loss, electric field distortion, and increased breakdown strength at high temperatures.