Abstract
In this study, the effects of three processing stages: filament extrusion, 3D printing (FDM), and hot-pressing are investigated on electrical conductivity and tensile mechanical properties of poly(lactic) acid (PLA) composites filled with 6 wt.% of multiwall carbon nanotubes(MWCNTs), graphene nanoplatelets (GNPs), and combined fillers. The filaments show several decades’ higher electrical conductivity and 50–150% higher values of tensile characteristics, compared to the 3D printed and the hot-pressed samples due to the preferential orientation of nanoparticles during filament extrusion. Similar tensile properties and slightly higher electrical conductivity are found for the hot-pressed compared to the 3D printed samples, due to the reduction of interparticle distances, and consequently, the reduced tunneling resistances in the percolated network by hot pressing. Three structural types are observed in nanocomposite filaments depending on the distribution and interactions of fillers, such as segregated network, homogeneous network, and aggregated structure. The type of structural organization of MWCNTs, GNPs, and combined fillers in the matrix polymer is found determinant for the electrical and tensile properties. The crystallinity of the 3D printed samples is higher compared to the filament and hot-pressed samples, but this structural feature has a slight effect on the electrical and tensile properties. The results help in understanding the influence of processing on the properties of the final products based on PLA composites.
Highlights
In the last years, a growing interest has been found in the research of graphene and carbon nanotube reinforced polymer nanocomposites with superior properties for a variety of applications
In this study, the effects of three processing stages: filament extrusion, 3D printing (FDM), and hot-pressing are investigated on electrical conductivity and tensile mechanical properties of poly(lactic) acid (PLA) composites filled with 6 wt.% of multiwall carbon nanotubes(MWCNTs), graphene nanoplatelets (GNPs), and combined fillers
In the present study, we investigate the electrical and tensile properties of PLA nanocomposites with graphene-carbon nanotube fillers influenced by three important processing stages: Nanomaterials 2020, 10, 35 filament extrusion, 3D printing, and hot-pressing
Summary
A growing interest has been found in the research of graphene and carbon nanotube reinforced polymer nanocomposites with superior properties for a variety of applications. Researchers found that the construction of a segregated structure by incorporating a small amount of highly conductive nanoparticles, such as carbon nanotubes and graphene in a polymer matrix, could fabricate composites with improved electrical conductivity at low percolation threshold over traditional randomly distributed composites [6]. Such segregated nanocomposites are usually prepared either by dispersion of filler in polymer blends or by the wrapping of polymer powder with nanoplatelets, such as carbon nanotubes and graphene followed by compressive molding [6]. Shi et al [7] adopted a local enrichment strategy for the preparation of highly conductive PLA-carbon nanotube composites with segregated structure by extrusion
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