Absorption Dominated Electromagnetic Interference Shielding Properties of Polylactic Acid/Polycaprolactone Composites With Electromagnetic Multilayered Structure

The reflective dominant electromagnetic interference (EMI) shielding performances of biodegradable polylactic acid (PLA) have seriously limited its application in electrical and electronic fields. Imidazolium polyurethane (IPU) modified carbon nanotubes (CNTs) and nickel@carbon nanotubes (Ni@CNTs) were used to improve the PLA/PCL composites' EMI shielding properties. The EMI shielding effectiveness (SE) of all samples increased with increasing CNTs and IPU2 content. The values of PLA5/PCL5 and PLA7/PCL3 composites with 10 wt% CNTs are 36.7 dB and 34.1 dB, and the reflection coefficient (R) of the samples is less than 0.5. IPU1 modified Ni@CNTs is selectively distributed at the PCL phase for the magnetic effect, and IPU2 modified CNTs are mainly located at the interface of the co-continuous structure, establishing a more complete three-dimensional conductive network. By constructing a dispersed structure of magnetic conductive fillers and a continuous structure of conductive fillers, absorptive dominant EMI shielding materials are realized through an electromagnetic multilayered structure. The addition of Ni@CNTs greatly enhanced the electromagnetic absorption, as well as the three-dimensional conductive network formed by CNTs, which can enhance electromagnetic attenuation. Plenty of interfaces in the co-continuous structure facilitated the multiple reflections of electromagnetic waves, thus achieving low-reflection electromagnetic shielding.