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.

This research presents a comprehensive investigation of PLA/PCL polymer blends using advanced rheological characterization, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and dynamic mechanical, thermal analysis (DMTA) to evaluate phase-separation behavior and functional properties. Polymer composites with various PLA/PCL ratios were fabricated via melt extrusion, a sustainable and scalable approach. The rheological studies revealed significant insights into the blends’ viscoelastic behavior, while SEM analyses provided detailed observations of microstructural phase separation. Thermal transitions and crystallization behaviors were evaluated through DSC, and the dynamic mechanical properties were examined via DMTA. The results confirmed that the tailored PLA/PCL blends exhibit properties suitable for advanced additive manufacturing (AM) and shape memory applications, merging flexibility and environmental sustainability. This study emphasizes the novelty of integrating multidisciplinary characterization methods to unravel the structure–property relationships in PLA/PCL systems. By addressing modern demands for eco-friendly, high-performance materials, this work establishes a foundation for the development of innovative polymer composites with potential applications in smart and responsive technologies.

The incorporation of small amount of hard and soft carbon nanofillers, such as nanoscale diamond, carbon ash and multiwall carbon nanotubes (MWCNT) have different effect on the surface properties of the neat polyester resin and polypropylene. The soft nanofiller, carbon ash did not influence the wear properties of the polyester resin up to 5 wt% filler content. In contrast, 0.5-5 wt% hard nanodiamond strongly decreased the wear mass loss of the polyester resin. The scratch resistance and the coefficient of friction of the polypropylene is improved significantly while there is 0.1-3 wt% MWCNT. Small amount of MWCNTs change significantly the molecular structure of the polypropylene, producing a nucleation effect. This was found to assist in the changes of surface prop- erties by increasing the hardness, friction and wear of polypropylene.

The present work deals with the mixing of two green polymers at several definite ratios that led to the receiving of biodegradable polylactic acid (PLA)/polycaprolactone (PCL) blends possessing well-expressed macromechanical and shape memory properties. Four non-compatibilized polymer compositions were prepared by using a twin-screw melt extrusion technique, allowing for a homogeneous dispersion of the PCL droplets in the PLA matrix and higher interfacial adhesion between the two phases. The mechanical behavior of the specimens was estimated by tensile experiments conducted at three particular crosshead velocities. It was established that the addition of PCL as a soft segment redounded to an increment of the toughness and elongation at ultimate strength of the polymer composite at the expense of the maximum tensile stress and Young’s modulus. These latter two parameters were found to be more sensitive, in terms of reaching high values, to the content of PLA as a hard segment in the polymer blend. Performing thermoresponsive shape memory tests disclosed an overwhelming reversibility between the temporary and permanent states of the composite materials, including significant shape fixation ($R_f$) and shape recovery ($R_r$) rates. SEM analysis of the PLA/PCL compositions revealed a distinct phase-separated microstructure, confirming the immiscibility of the two polymers in the blend.

The investigation of new composite materials possessing low weight but not at the expense of their mechanical performance is of great interest in terms of reducing energy consumption in many industrial applications. This study is focused on the nanomechanical characterization of high-density polyethylene (HDPE)-based composite specimens modified with equal loadings of graphene nanoplatelets (GNPs) and/or multiwall carbon nanotubes (MWCNTs). Quasi-static nanoindentation analysis revealed the impact of the carbon nanofillers on the receiving of nanocomposites with higher nanohardness and reduced modulus of elasticity, reaching values of 0.146 GPa and 3.57 GPa, respectively. The role of the indentation size effect in elastic polymer matrix was assessed by applying three distinct peak forces. Nanoscratch experiments depicted the tribological behavior of the composite samples and inferred the influence of the carbon nanofillers on the values of the coefficient of friction (COF). It seems that the incorporation of 4 wt% GNPs in the polymer structure improves the scratch resistance of the material, resulting in a higher value of the exerted lateral force and therefore leading to the detection of a higher coefficient of friction at scratch of 0.401. A considerable pile-up response of the scratched polymer specimens was observed by means of in-situ SPM imaging of the tested surface sample area. The sway of the carbon nanoparticles on the composite pile-up behavior and the effect of the pile-up on the measured friction coefficients have been explored.

Biodegradable nanocomposite materials possessing self-healing behavior are emerging as an attractive option of being used in advanced mechatronic systems. The current study is focused on a thorough examination of the micromechanical properties of graphene–reinforced polylactic acid (PLA)/polycaprolactone (PCL) composite samples, followed by estimation of their self-healing behavior upon heating. Polymer blend–based nanocomposite materials were prepared using the green and reliable in terms of good nanofiller dispersion melt extrusion method. 3D printed nanocomposite specimens with impeccable flatness were subjected to fine microscratch testing by applying a constant force experimental mode. The surface resistance of the three-component polymer materials against the lateral movement of the stylus fulfilling the scratch and the impact of the dual-phase PLA/PCL ratio on the nanocomposite mechanical performance were estimated by calculation of the coefficient of friction (COF = F_x/F_z). COF values in the range of 0.8–1.4 indicated excellent nanocomposite resilience against scratch. Creating a heterogeneous polymer system that combines phase-separated soft and hard domains with close melt and glass transition temperatures, respectively, may facilitate the physical flow of macromolecular chains into voids or free volume areas. This aspect can be critical in the achievement of thermally–induced self-healing properties of the composite material. Scanning electron microscopy (SEM) imaging of the microscratches, made before and after Joule heating of the polymer samples, revealed a significant degree of surface recovery and a sensible reduction in the width of the adjusted scratch grooves.