Tuning PVDF nanocomposite crystallinity, mechanical properties, and EMI shielding via solvent ratio control for manufacturing efficient multilayer structures

With the rapid expansion of electronic technologies, electromagnetic (EM) pollution has become a major concern, threatening device performance and human health. In this study, thin and flexible PVDF-based nanocomposite films containing 5 wt% graphene oxide (GO) and 5 wt% carbon nanotubes (CNT) showed high electromagnetic interference shielding effectiveness (EMI SE) and absorption for EMI protection. The films were fabricated via solution casting using an acetone/dimethylformamide (DMF) mixed solvent system. The solvent ratio strongly influenced crystallinity, dispersion, and electrical conductivity, thereby affecting EMI SE. At 70 vol% acetone, the PVDF/CNT/GO film achieved an average EMI SE of 20.9 dB and a normalized EMI SE (SE/t) of 131.1 dB/mm, with a reflectance coefficient of 0.85 and conductivity of 1.5 S/m. Building on these results, multilayer structures were designed to reduce reflectance and enhance EMI SE, mitigating secondary EMI pollution. A four-layer structure composed of PVDF/CNT/GO and PVDF/GO conductive layers separated by PVDF spacers showed superior performance. The multilayer structure was fabricated by a simple stacking method using PVDF solution as binder at room temperature, eliminating hot-press or compression molding, reducing energy consumption, and preserving filler distribution. The resulting structure achieved an SE/t of 40.8 dB/mm at a thickness of 0.6 mm and a reduced reflectance ratio of 0.55. The multilayer films exhibited ductile mechanical behavior with a yield strength of 10 MPa and strain at break of 80%. Furthermore, their strain-sensing capability with a gauge factor of 143.5 suggests potential use for flexible and sensitive film applications. Overall, this study presents a lightweight, flexible, and robust EMI shielding films for advanced electromagnetic protection applications.