Electromagnetic properties of filaments containing nanofillers for 3d printing

PLA filaments filled with different percentages of commercial graphene nanoplates (GNP) and multi-walled carbon nanotubes (CNT), produced for Fused Deposition Modeling (FDM) 3D-printing, are here considered. In particular, the electromagnetic properties of the filament obtained with two different processes are compared in order to assess the influence of the different procedures, named solution blending (SB) and melt extrusion (ME), on the Ka-band (26-37 GHz) behavior of the nanocomposites. First, the method of measurements of electromagnetic response of rod-shaped samples in the instrumentation waveguide is studied and implemented. Then, the electromagnetic properties of filaments loaded with nanocomposites in a maximum of 6wt% are investigated, assuming for each filler the possible value of {0,3,6} wt%. The experimental results in terms of reflection and absorption are used to estimate the complex permittivity and the AC electrical conductivity in samples under study by using a suitable created code. Filaments prepared by ME show higher values of both components of dielectric permittivity compared to SB. The highest values of relative permittivity are obtained for the bi-filler filament (3wt% GNP and 3wt% CNT) in ME processes (max value 12.73), whereas a maximum of 11.84 is reached for the relative permittivity of SB produced filament. Maximal AC conductivity is observed for composites containing 6wt% of GNP and 6wt% of CNT for SB and ME respectively. Electrical percolation thresholds (EPT) consistent with literature available DC results are detected, ranging in the explored filler amount, except for the SB produced CNT-based filament.