Abstract
The limitation of poor mechanical stability and difficulties in printing electrically conductive components can be overcome owing to the recent introduction of nanotechnology into the field of additive manufacturing (AM) and the consequent development of nonconventional polymer nanocomposites suitable for 3D printing. In the present work, different weight percentages (up to 6 wt % in total) of carbon-based nanostructures—multiwalled carbon nanotubes (MWCNTs), graphene nanoplatelets (GNPs), and a combination of both fillers (MWCNTs/GNPs)—were incorporated into poly(lactic) acid (PLA, Ingeo™) in an attempt to overcome several limitations of conventional 3D manufacturing based on insulating materials. Solution blending and melt mixing were the two fabrication methods adopted for preparation of the samples under test. A comparison of the morphological, rheological, and electrical properties of the resulting nanocomposites was carried out. Moreover, for the same weight concentrations, the influence of physical and geometrical features (i.e., functionalization and aspect ratio) of the embedded fillers was also investigated. Rheological methods were applied to control the quality of fillers dispersion in PLA matrix. The rheological percolation threshold was considered as reference in order to evaluate the internal structure of nanodispersions. TEM visualization, combined with rheological characterizations, was used for efficient control of the nanofiller dispersion. DC characterization revealed that lower electrical percolation thresholds and higher values of electrical conductivity were achieved using fillers with a larger aspect ratio and melt mixing, respectively. Moreover, given the possibility of obtaining complex and appropriate shapes for electromagnetic compatibility (EC) applications, electromagnetic (EM) response of the nanocomposites at the highest filler concentration was investigated in GHz and THz regions. It was found that the electromagnetic shielding efficiency (EMI) of nanocomposites strongly depended on the aspect ratio of the nanofillers, whereas the type of processing technique did not have a significant effect. Therefore, a careful choice of methods and materials must be made to address the final application for which these materials and further 3D printed architectures are designed.
Highlights
Among the most widely used techniques of 3D printing (3DP), such as selective laser sintering (SLS) [2], solvent-cast 3DP (SC3DP) [3], UV-assisted 3DP (UV3DP) [4], stereo-lithography [5], and fused deposition modeling (FDM), the latter seems to be one of the most promising given its simplicity and potential applicability [6,7]
This remarkable difference could be explained by the fact that many parameters, such as the filler aspect ratio, functionalization, dispersion state, and tendency to agglomerate, as well as the fabrication process, the nature of matrix, and its interaction with the reinforcement, have been demonstrated to affect the percolation threshold of conducting polymer composites based on electrically percolating networks
Nonconventional thermoplastic composites of poly(lactic) acid filled with highly conductive nanocarbon materials—pure and functionalized multiwalled carbon nanotubes (MWCNTs), graphene nanoplatelets (GNPs), and a combination of both fillers—were produced using two different approaches: solution blending and melt mixing
Summary
Among the most widely used techniques of 3D printing (3DP), such as selective laser sintering (SLS) [2], solvent-cast 3DP (SC3DP) [3], UV-assisted 3DP (UV3DP) [4], stereo-lithography [5], and fused deposition modeling (FDM), the latter seems to be one of the most promising given its simplicity and potential applicability [6,7]. An improvement in the quality of the final product has been observed due to the lower temperatures required to sinter and extrude the printed parts [9,10] Due to their excellent electrical conductivity combined with good mechanical and thermal properties, carbon-based fillers like carbon nanotubes (CNTs), nanofibers (CNFs), and graphene are embedded in host polymeric matrices characterized by easy processability and shaping possibilities in order to obtain new resulting materials with improved and tailored properties [11,12]. This is attractive for solving electromagnetic compatibility (EC) problems due to the good electrical conductivity achieved and the opportunity to create geometrically complex structures driven by computer-aided design (CAD) specifications [24]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
