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This study developed a novel 3D-printable poly(vinylidene fluoride) (PVDF)-based nanocomposite incorporating 6 wt% graphene nanoplatelets (GNPs) with programmable characteristics for resistive heating applications. The results highlighted the significant effect of a controlled printing direction (longitudinal, diagonal, and transverse) on the electrical, thermal, Joule heating, and thermo-resistive properties of the printed structures. The 6 wt% GNP/PVDF nanocomposite exhibited a high electrical conductivity of 112 S·m−1 when printed in a longitudinal direction, which decreased significantly in other directions. The Joule heating tests confirmed the material's efficiency in resistive heating, with the maximum temperature reaching up to 65 °C under an applied low voltage of 2 V at a raster angle of printing of 0°, while the heating Tmax decreased stepwise with 10 °C at the 45° and the 90° printing directions. The repeatability of the Joule heating performance was verified through multiple heating and cooling cycles, demonstrating consistent maximum temperatures across several tests. The effect of sample thickness, controlled by the number of printed layers, was investigated, and the results underscore the advantages of programmable 3D printing orientation in thin layers for enhanced thermal stability, tailored electrical conductivity, and efficient Joule heating capabilities of 6 wt% GNP/PVDF composites, positioning them as promising candidates for next-generation 3D-printed electronic devices and self-heating applications. [ABSTRACT FROM AUTHOR]

Nowadays, a strong demand exists for printable materials with multifunctionality and proper rheological properties to overcome the limitations to deposit layer-by-layer in additive extrusion. The present study discusses rheological properties related to the microstructure of hybrid poly (lactic) acid (PLA) nanocomposites filled with graphene nanoplatelets (GNP) and multiwall carbon nanotubes (MWCNT) to produce multifunctional filament for 3D printing. The alignment and slip effects of 2D-nanoplatelets in the shear-thinning flow are compared with the strong reinforcement effects of entangled 1D-nanotubes, which govern the printability of nanocomposites at high filler contents. The mechanism of reinforcement is related to the network connectivity of nanofillers and interfacial interactions. The measured shear stress by a plate–plate rheometer of PLA, 1.5% and 9% GNP/PLA and MWCNT/PLA shows an instability for high shear rates, which is expressed as shear banding. A rheological complex model consisting of the Herschel–Bulkley model and banding stress is proposed for all considered materials. On this basis, the flow in the nozzle tube of a 3D printer is studied by a simple analytical model. The flow region is separated into three different regions in the tube, which match their boundaries. The present model gives an insight into the flow structure and better explains the reasons for printing enhancement. Experimental and modeling parameters are explored in designing printable hybrid polymer nanocomposites with added functionality. [ABSTRACT FROM AUTHOR]

Polylactic acid (PLA) containing 12 wt% of nanofillers, such as multi‐walled carbon nanotubes (MWCNTs), graphene nanoplates (GNPs), is considered to obtain a non‐conventional filament suitable for additive manufacturing (AM) process with enhanced thermal and electrical properties. In details, three‐dimensional (3D) printed specimens obtained by means of fused deposition modeling (FDM) are experimentally characterized in terms of thermal conductivity and relative permittivity. The results are interpreted on the basis of the different features of the fillers and their interaction with the PLA, as evidenced by a morphological analysis. It is found better thermal transport by using two‐dimensional (2D) shape nanoparticles (GNPs) with an improvement of about 260% respect to the unfilled polymer most likely due to its favorable arrangement and the lower thermal boundary resistance between the two phases, matrix, and fillers. Differently, mono‐dimensional filler like MWCNTs is to be preferred in order to obtain higher value for the relative permittivity, due to the enhancement of the interfacial polarization and the presence of functionalized groups. It is found a value of 5.35 × 103 much greater than that of 3.7 measured for pure PLA. Given the good combined thermal and dielectric properties, such materials are promising candidates for packaging applications with electromagnetic (EM) shielding capability. [ABSTRACT FROM AUTHOR]

Influences of different nanocomposite loadings in poly(lactic acid) (PLA) matrix on resulting hardness and elasticity were examined in nanoindentation experiments. The following study was focused on the nanomechanical properties of PLA reinforced with graphene nanoplatelets (GNPs) and multiwall carbon nanotubes (MWCNTs) by using Berkovich type pyramidal nanoindenter. A masterbatch strategy was developed to disperse GNP and MWCNT into PLA by melt blending. Young's modulus and nanohardness of as‐prepared nanocomposites were characterized as a function of the graphene and carbon nanotubes loading. The nanoindentation analysis reveals that these carbon nanofillers improve the mechanical stability of the nanocomposites GNP/PLA, MWCNT/PLA, and GNP/MWCNT/PLA. That improvement of mechanical properties strongly depends on the fillers content. It was found that the best mechanical performance was achieved for the compound having 6 wt % graphene and 6 wt % MWCNTs in the PLA matrix. The received values for nanohardness and Young's modulus are among the highest reported for PLA‐based nanocomposites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47260. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract This paper aims to address current limitations of 3D printed conductive materials through the development of a novel formulation of a thermoplastic composite. In particular, a conductive filament suitable for three-dimensional printing is obtained on the basis of Polylactic acid (PLA) filled with two types of highly conductive nano-carbon materials, i.e. multi-walled carbon nanotubes (MWCNTs), graphene nanoplates (GNPs) and a combination of both fillers (MWCNT/GNP). A systematic rheological and electrical characterization of the resulting nanocomposites is presented. Viscoelastic properties and rheological percolation threshold are determined for the binary and ternary composites and related to the size of nanoparticles. Comparable values for the percolation threshold are found by means of rheological and electrical studies. Low electrical percolation thresholds and high values of the electrical conductivity of the order of S/m are achieved for the investigated formulations. At the highest filler loading (i.e. 12 wt%) the electrical conductivity reaches the value of 4.54 S/m, 6.27 S/m and 0.95 S/m for the composites based on MWCNTs, GNPs and multiphase system, respectively. These results, together with the good stability shown by the nano-reinforced PLA in the frequency range [100 Hz-1MHz] make these composites promising candidates for 3D printed conductive devices for electromagnetic (EM) applications. [ABSTRACT FROM AUTHOR]