Thermo‑mechanical properties and electrical mapping of nanoscale domains of carbon‑based structural resins

Carbon nanostructured forms, such as one-dimensional (1D) carbon nanofbers (CNFs) and two-dimensional (2D) graphene nanoplatelets (GNPs), are increasingly attracting the attention of scientists whose studies are aimed at obtaining superior nanocomposites with unrivaled performance and/or unprecedented properties. In this work, nanocomposites loaded with diferent mass percentages of carbonaceous nanoparticles (CNFs, GNPs) capable to exhibit discrete electrical conductivity have been investigated using diferential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and tunneling atomic force microscopy (TUNA). DSC and DMA investigations highlighted that an appropriate chemical composition of the hosting matrix, together with a suitable two-stage curing cycle allows formulating structural resins characterized by high values of the curing degree (higher than 97%), glass transition temperature (also higher than 250 °C), and storage modulus (higher than 3000 MPa at room temperature). TUNA analysis evidences a satisfactory distribution of the conductive nanofller on nanometric domains

Electrical conductivity of carbon nanofiber reinforced resins: potentiality of Tunneling Atomic Force Microscopy (TUNA) technique

Epoxy nanocomposites able to meet pressing industrial requirements in the field of structural material have been developed and characterized. Tunneling Atomic Force Microscopy (TUNA), which is able to detect ultra-low currents ranging from 80 fA to 120 pA, was used to correlate the local topography with electrical properties of tetraglycidyl methylene dianiline (TGMDA) epoxy nanocomposites at low concentration of carbon nanofibers (CNFs) ranging from 0.05% up to 2% by wt. The results show the unique capability of TUNA technique in identifying conductive pathways in CNF/resins even without modifying the morphology with usual treatments employed to create electrical contacts to the ground

Carbon-Based Aeronautical Epoxy Nanocomposites: Effectiveness of Atomic Force Microscopy (AFM) in Investigating the Dispersion of Different Carbonaceous Nanoparticles

The capability of Atomic Force Microscopy (AFM) to characterize composite material interfaces can help in the design of new carbon-based nanocomposites by providing useful information on the structure−property relationship. In this paper, the potentiality of AFM is explored to investigate the dispersion and the morphological features of aeronautical epoxy resins loaded with several carbon nanostructured fillers. Fourier Transform Infrared Spectroscopy (FTIR) and thermal investigations of the formulated samples have also been performed. The FTIR results show that, among the examined nanoparticles, exfoliated graphite (EG) with a predominantly two-dimensional (2D) shape favors the hardening process of the epoxy matrix, increasing its reaction rate. As evidenced by the FTIR signal related to the epoxy stretching frequency (907 cm−1), the accelerating effect of the EG sample increases as the filler concentration increases. This effect, already observable for curing treatment of 60 min conducted at the low temperature of 125 °C, suggests a very fast opening of epoxy groups at the beginning of the cross-linking process. For all the analyzed samples, the percentage of the curing degree (DC) goes beyond 90%, reaching up to 100% for the EG-based nanocomposites. Besides, the addition of the exfoliated graphite enhances the thermostability of the samples up to about 370 °C, even in the case of very low EG percentages (0.05% by weight)

Electrical conductivity of carbon nanofiber reinforced resins: Potentiality of Tunneling Atomic Force Microscopy (TUNA) technique

Epoxy nanocomposites able to meet pressing industrial requirements in the field of structural material have been developed and characterized. Tunneling Atomic Force Microscopy (TUNA), which is able to detect ultra-low currents ranging from 80 fA to 120 pA, was used to correlate the local topography with electrical properties of tetraglycidyl methylene dianiline (TGMDA) epoxy nanocomposites at low concentration of carbon nanofibers (CNFs) ranging from 0.05% up to 2% by wt. The results show the unique capability of TUNA technique in identifying conductive pathways in CNF/resins even without modifying the morphology with usual treatments employed to create electrical contacts to the ground

Toughening of epoxy adhesives by combined interaction of carbon nanotubes and silsesquioxanes

The extensive use of adhesives in many structural applications in the transport industry and particularly in the aeronautic field is due to numerous advantages of bonded joints. However, still many researchers are working to enhance the mechanical properties and rheological performance of adhesives by using nanoadditives. In this study the effect of the addition of Multi-Wall Carbon Nanotubes (MWCNTs) with Polyhedral Oligomeric Silsesquioxane (POSS) compounds, either Glycidyl Oligomeric Silsesquioxanes (GPOSS) or DodecaPhenyl Oligomeric Silsesquioxanes (DPHPOSS) to Tetraglycidyl Methylene Dianiline (TGMDA) epoxy formulation, was investigated. The formulations contain neither a tougher matrix such as elastomers nor other additives typically used to provide a closer match in the coefficient of thermal expansion in order to discriminate only the effect of the addition of the above-mentioned components. Bonded aluminium single lap joints were made using both untreated and Chromic Acid Anodisation (CAA)-treated aluminium alloy T2024 adherends. The effects of the different chemical functionalities of POSS compounds, as well as the synergistic effect between the MWCNT and POSS combination on adhesion strength, were evaluated by viscosity measurement, tensile tests, Dynamic Mechanical Analysis (DMA), single lap joint shear strength tests, and morphological investigation. The best performance in the Lap Shear Strength (LSS) of the manufactured joints has been found for treated adherends bonded with epoxy adhesive containing MWCNTs and GPOSS. Carbon nanotubes have been found to play a very effective bridging function across the fracture surface of the bonded joints

A novel fully human antitumour immunoRNase targeting ErbB2-positive tumours

BACKGROUND: ErbB2 is an attractive target for immunotherapy, as it is a tyrosine kinase receptor overexpressed on tumour cells of different origin, with a key role in the development of malignancy. Trastuzumab, the only humanised anti-ErbB2 antibody currently used in breast cancer with success, can engender cardiotoxicity and a high fraction of patients is resistant to Trastuzumab treatment. METHODS: A novel human immunoRNase, called anti-ErbB2 human compact antibody-RNase (Erb-hcAb-RNase), made up of the compact anti-ErbB2 antibody Erbicin-human-compact Antibody (Erb-hcAb) and human pancreatic RNase (HP-RNase), has been designed, expressed in mammalian cell cultures and purified. The immunoRNase was then characterised as an enzymatic protein, and tested for its biological actions in vitro and in vivo on ErbB2-positive tumour cells. RESULTS: Erb-hcAb-RNase retains the enzymatic activity of HP-RNase and specifically binds to ErbB2-positive cells with an affinity comparable with that of the parental Erb-hcAb. Moreover, this novel immunoRNase is endowed with an effective and selective antiproliferative action for ErbB2-positive tumour cells both in vitro and in vivo. Its antitumour activity is more potent than that of the parental Erb-hcAb as the novel immunoconjugate has acquired RNase-based cytotoxicity in addition to the inhibitory growth effects, antibody-dependent and complement-dependent cytotoxicity of Erb-hcAb. CONCLUSION: Erb-hcAb-RNase could be a promising candidate for the immunotherapy of ErbB2-positive tumours

Heat transport in tetra-functional epoxy resin containing low percentage of exfoliated graphite nanoparticles

Thermal management with conductive polymeric nano-composites has become a central task of industrial interest for many applications ranging from exchangers in electric and electronic systems to electronic packaging and photovoltaic devices. In order to enhance the thermal conductivity of polymeric composites there is a tendency to incorporate thermally conductive nano-fillers in the polymeric matrix. Actually the most widely used are the carbon nanotubes (CNTs) due to their outstanding mechanical, electrical and thermal properties together with a high aspect ratio and surface area. The incorporation of CNTs into the polymer matrix has significantly enhanced mechanical and electrical performance of final composite material but until now the desired enhancement in thermal conductivity has not been achieved. The aim of this work is to carry out a preliminary experimental investigation of thermal properties and heat conduction in epoxy nanocomposites prepared by dispersing low concentrations of different kinds of nanofillers, such as 1-D multiwall carbon nanotubes and 2-D predominant shape exfoliated graphite (EG) within an aeronautic resin based on a tetrafunctional epoxy precursor. For the analyzed epoxy formulations the best results are obtained using EG as nanofillers. The curing degree for the EG-based epoxy nanocomposites cured up to 200°C is very high compared to unfilled epoxy resin, reaching up to 100%. EG nanoparticles also accelerate the curing process of the epoxy resin of about 20°C and this is most likely due to better phonon conduction through carbonaceous nanostructures with predominantly two-dimensional flat shape. This is confirmed by experimental values of thermal conductivity that show an increase of 300% for 3% of Exfoliated Graphite embedded in tetrafunctional epoxy resin. In light of these results it is clearly evident the potential of 2-D graphene sheets as promising nanofillers able to meet the ambitious requirements in the thermal management for high-performance nanocomposites

Corso di lingua e cultura italiana 1

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