Carbon nanofibers (CNFs), graphene platelets (GPs), and their mixtures were treated by plasma polymerization of propylene. The carbon nanoparticles (CNPs) were previously sonicated in order to deagglomerate and increase the surface area. Untreated and plasma treated CNPs were analyzed by dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and thermogravimetric analysis (TGA). DLS analysis showed a significant reduction of average particle size, due to the sonication pretreatment. Plasma polymerized propylene was deposited on the CNPs surface; the total amount of polymerized propylene was from 4.68 to 6.58 wt-%. Raman spectroscopy indicates an increase in the sp 3 hybridization of the treated samples, which suggest that the polymerized propylene is grafted onto the CNPs.

Carbon nanofibers (CNFs) are surface-modified by plasma polymerization using ethylene as monomer. The modified CNFs are suitable to be mixed with different polyethylenes. In this study, we mix them with high density polyethylene (HDPE). The plasma-coated CNFs (pCNFs) are then characterized by Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), and Scanning Electron Microscopy (SEM) in the transmission mode (STEM). Treated and untreated CNFs are evaluated in water, chloroform, and 1,2,3-trichlorobenzene (TCB) to evaluate their effective dispersion in these three solvents. FTIR spectra showed signals corresponding to the organic part deposited on the surface of pCNFs. The TGA analysis makes it possible to confirm that pCNFs have a higher weight loss than CNFs because of the volatilization of the plasma polymerized ethylene coating. Dispersion tests showed that pCNFs dispersed well in TCB and chloroform solvents. To prepare nanocomposites, HDPE and CNFs are mixed well in a single-screw extruder with an attached sonication chamber at its exit. Nanocomposites containing 1% and 3% by weight of CNFs are prepared. The products are analyzed by the Young's modulus and evaluated for thermal stability.

Thermal conductivity of epoxy resins was highly improved (up to 1.95 W/mK) with the addition of 7, 10, and 15 wt% of a hybrid filler composed of 70-30 wt % ratio of graphene and copper nanoparticles, respectively. Hybrid filler was obtained by high energy mechanical milling in two manners; just the two nanoparticles "dry milling" and with the addition of ethylene-glycol "wet milling." The crystalline structure was severely destroyed with dry milling but not with wet milling. Wet milling was thereafter used to obtain the hybrid filler that was later used in producing the epoxy nanocomposites. Raman spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and electron microscopy were used to determine the interaction between both nanoparticles in the obtained hybrid graphene-copper filler. XPS findings suggest that certain amount of copper is bonded to the graphene surface nanoparticles. This bonding could be carried out by the charge-transfer interaction between graphene and copper or by physisorption of copper between the graphene nanosheets. The signals in 119.2 and 120.7 eV, observed in the deconvolution of Cu3s signal, correspond to copper carbon bonds Cu═C and Cu C, respectively. This "wet" mechanical milling methodology represents a good option to prepare graphene/metal (hybrid) fillers.

Addition of different contents of ground tire rubber (GTR) of different particles size in crosslinked-foamed compounds based on low density polyethylene (LDPE)/ethylene vinyl acetate (EVA) was studied. Compounds were made by melt mixing in an internal mixer at 100°C and 60 rpm. Trigonox 145-45B as crosslinking agent, azodicarbonamide (ADC) as chemical blowing agent (CBA) and ZnO/SiO2as foaming co-agents, were used. GTR of 149, 74, and 44 μm particle size was incorporated as “cell nucleating agent”, each particle size at 5, 10, and 20 phr. Morphological parameters such as average cell size (d), cell size distribution and cellular density (NC) were evaluated from images acquired by scanning electron microscopy (SEM). The results obtained from the SEM characterization show a significant reduction ofd, a significance increment onNC, up to 5.81*105to 3.62*107cells/cm3and a better homogenization of the cell size distribution in the foamed compounds with high GTR contents of the smaller particle size.

Agave fibers (AF) were incorporated either pristine (AFp) or surface treated by ethylene plasma (AFm) in low-density polyethylene (LDPE)/ethylene vinyl acetate (EVA) blends at a ratio of 1 : 1 and foamed by chemical means. The role of the AF content (3, 6, 9, 12, and 15 wt.%) and its surface modification on the cellular morphology and mechanical properties of LDPE/EVA/AF foams under compression is investigated herein. Fourier transform-infrared spectroscopy, contact angle, and water suspension of AF suggest that plasma treatment using ethylene successfully modifies the surface nature of AF from hydrophilic to hydrophobic. AF and the surface treatment have an important role on the morphological properties of the foams. Composite foams reinforced with 12 wt.% AFm exhibited the highest mechanical properties improvements. At this fiber content, the composite foams enhanced 30% of the compressive modulus and 23% of the energy absorption under compression with respect to the neat polymer blend foam, as a result to the formation of more uniform cells with smaller size and the enhancement of compatibility and spatial distribution of the AFm in the polymer composite foams due to thin clusters of polyethylene-like polymer deposited on the AF surface.

Graphic abstract Graphene decorated with cooper nanostructures were prepared with and without ionic liquid (IL) using different milling times. The obtained samples were characterized by Raman, X-ray diffraction (XRD) and transmission electron microscopy (TEM), to analyze the effect of the grinding time on the copper particles adhesion to the graphene sheets. Composites of silicon with two contents of G/Cu, at two weight ratios, nanostructures were prepared and the crosslinking characteristics were analyzed by a rubber process analyzer. The thermal conductivity, electrical resistivity and antimicrobial characteristics against E. coli and S. aureus for these silicon/G/Cu composites were determined. It was found that the use of IL enhances the G/Cu nanostructures dispersion into the silicon polymer matrix with a noticeable improvement in thermal conductivity of 1.12 W/mK for a 7 wt% of G/Cu, a volume electrical resistivity of 4.1 × 10 10 Ω cm with 7 wt% of G/Cu nanoparticles and antimicrobial response of 4.21 ± 0.11 to E. coli and 5.33 ± 0.11 to S. aureus with 7% of G/Cu nanoparticles. It was determined that π–π interactions between graphene and aromatic molecule of IL may be influencing the observed improvement in G/Cu dispersion and final composite performance. The novelty of this work is the use of IL to improve the G/Cu NPs dispersion into the silicon polymer matrix. This silicon/G/Cu composite could be an option to prepare medical devices for electrotherapy or face protection against COVID-19 or other silicon-based devices for medical applications.

No abstract

No abstract