Injection-molded microcellular PLA/graphite nanocomposites with dramatically enhanced mechanical and electrical properties for ultra-efficient EMI shielding applications

Abstract

High-performance EMI shielding materials with renewable characteristics are needed to address the issue of electromagnetic radiation pollution. The use of traditional metal-based EMI shielding materials is limited by their high density, corrosiveness, and expensive processing costs. At the same time, using regular fossil-fuel-driven conductive polymer composite-based EMI shielding materials creates environmental pollution, exacerbates resource consumption, and offers poor electromagnetic shielding effectiveness. Moreover, most of the processing methods used for conductive polymer composite-based EMI shielding materials are focused on a batch-scale process, which cannot easily be scaled up. We studied a sustainable foam injection molding-based method to efficiently fabricate renewable microcellular PLA/graphite nanocomposite foams, with improved mechanical and electrical properties for ultra-efficient EMI shielding applications. A microcellular PLA/graphite nanocomposite foam, with a density of 0.7 g cm⁻³ and a thickness of 2.0 mm, exhibits an outstanding EMI shielding performance with a total electromagnetic interference shielding effectiveness (EMI SE) of up to 45 dB. More importantly, thanks to the reduced reflection, which resulted from the strong thin-film interference effect, this lightweight porous nanocomposite foam has an absorption-dominated EMI shielding feature with a radiation energy reflection of less than 15%. The nanographite reorientation, which resulted from foaming, led to the microcellular PLA/graphite nanocomposite foam's electrical conductivity being dramatically increased by almost six orders of magnitude, in relation to the unfoamed sample. Furthermore, the microcellular PLA/graphite nanocomposite foam also exhibited outstanding mechanical properties. These were characterized by a strong specific strength and modulus, and super-ductile fracture behavior. Thus, this lightweight sustainable nanocomposite foam demonstrated great promise as an ultra-efficient EMI shielding material for future use in many applications such as aerospace and electronics.