Comparison of Branched and Linear Perfluoropolyether Chains Functionalization on Hydrophobic, Morphological and Conductive Properties of Multi-Walled Carbon Nanotubes

The functionalization of multi-walled carbon nanotubes (MW-CNTs) was obtained by generating reactive perfluoropolyether (PFPE) radicals that can covalently bond to MW-CNTs\u2019 surface. Branched and linear PFPE peroxides with equivalent molecular weights of 1275 and 1200 amu, respectively, have been thermally decomposed for the production of PFPE radicals. The functionalization with PFPE chains has changed the wettability of MW-CNTs, which switched their behavior from hydrophilic to super-hydrophobic. The low surface energy properties of PFPEs have been transferred to MW-CNTs surface and branched units with trifluoromethyl groups, CF3, have conferred higher hydrophobicity than linear units. Porosimetry discriminated the effects of PFPE functionalization on meso-porosity and macro-porosity. It has been observed that reactive sites located in MW-CNTs mesopores have been intensively functionalized by branched PFPE peroxide due to its low average molecular weight. Conductivity measurements at different applied pressures have showed that the covalent linkage of PFPE chains, branched as well as linear, weakly modified the electrical conductivity of MW-CNTs. The decomposed portions of PFPE residues, the PFPE chains bonded on carbon nanotubes, and the PFPE fluids obtained by homo-coupling side-reactions were evaluated by mass balances. PFPE-modified MW-CNTs have been characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), static contact angle (SCA), surface area, and porosity measurements

Italian WEEE management system and treatment of end-of-life cooling and freezing equipments for CFCs removal

This study presents and analyzes the data of the Italian system for take-back and recovery of waste electrical and electronic equipments (WEEEs) in the start-up period 2008–2010. The analysis was focused particularly on the data about the treatment of end-of-life cooling and freezing equipments. In fact, the wastes of cooling and freezing equipments have a high environmental impact. Indeed, in their compressor oil and insulation polyurethane (PU) foams chlorofluorocarbon (CFC) ozone-depleting gases are still present. In the period 2001–2004 Northern Italy resulted the main source in Europe of CFCs. The European Directive on WEEE management was enacted in 2002, but in Italy it was implemented by the legislative Decree in 2005 and it became operational in 2008. Actually, in 2008 the national WEEE Coordination Centre was founded in order to organize the WEEE pick-up process and to control collection, recovery and recycling targets. As a result, in 2010 the average WEEE collection per capita exceeded the threshold of more than 4 kg per inhabitant, as well as cooling and freezing appliances represented more than one fourth of the Italian WEEE collection stream. During the treatment of end-of-life cooling and freezing equipments, CFCs were recovered and disposed principally by burner methods. The analyses of defined specimens collected in the treatment facilities were standardized to reliably determine the amount of recovered CFCs. Samples of alkaline solid salt, alkaline saline solution, polyurethane matrix and compressor oil collected during the audit assessment procedure were analyzed and the results were discussed. In particular, the analysis of PU samples after the shredding and the warm pressing procedures measured a residual CFCs content around 500–1300 mg/kg of CFCs within the foam matrix

Surface modification of multi‐walled carbon nanotubes by perfluoropolyether peroxide

Multi-walled carbon nanotubes (MW-CNTs) were functionalized via covalent linkage of perfluoropolyether (PFPE) radicals obtained by thermal decomposition of linear PFPE peroxide, i.e. a macromolecular compound with a linear structure where (CF2CF2O), (CF2O) and peroxidic units were randomly distributed along the polymer chain. T O(CF2CF2O)m(CF2O)n(O)V T' + CF2O[(CF2CF2O)m (CF2O)n] T + V CF2O The PFPE-functionalized MW-CNTs were characterized by X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle (CA) and surface area measurements. The effects of the chemical treatment on the conductive properties of MW-CNTs were studied by resistivity measurements at different applied pressures. Moreover, the amount of PFPE chains linked on carbon nanotubes, the PFPE fluids obtained by homocoupling side-reactions and the decomposed portion of PFPE were evaluated by mass balances. After the introduction of PFPE chains on MW-CNTs surface, the water contact angle measured on molded pellets of modified MW-CNTs significantly increased over 150\ub0. This result revealed that the modification of MW-CNTs changed their wettability from a hydrophilic behavior to superhydrophobic, because the low surface energy properties of PFPE have been transferred to the MW-CNTs surface. From conductivity measurements we concluded that the covalent linkage of PFPE chains weakly influenced on electrical properties of conductive MW-CNTs. The experimental results indicated that fucntionalization with PFPE peroxide is a suitable technique to modify and control physical-chemical properties of MW-CNTs

Surface modification of multi-walled carbon nanotubes by perfluoropolyether peroxide

Multi-walled carbon nanotubes (MW-CNTs) were functionalized via covalent linkage of perfluoropolyether (PFPE) radicals obtained by thermal decomposition of linear PFPE peroxide, i.e. a macromolecular compound with a linear structure where (CF2CF2O), (CF2O) and peroxidic units were randomly distributed along the polymer chain. T O(CF2CF2O)m(CF2O)n(O)V T' + CF2O[(CF2CF2O)m (CF2O)n] T + V CF2O The PFPE-functionalized MW-CNTs were characterized by X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle (CA) and surface area measurements. The effects of the chemical treatment on the conductive properties of MW-CNTs were studied by resistivity measurements at different applied pressures. Moreover, the amount of PFPE chains linked on carbon nanotubes, the PFPE fluids obtained by homocoupling side-reactions and the decomposed portion of PFPE were evaluated by mass balances. After the introduction of PFPE chains on MW-CNTs surface, the water contact angle measured on molded pellets of modified MW-CNTs significantly increased over 150\ub0. This result revealed that the modification of MW-CNTs changed their wettability from a hydrophilic behavior to superhydrophobic, because the low surface energy properties of PFPE have been transferred to the MW-CNTs surface. From conductivity measurements we concluded that the covalent linkage of PFPE chains weakly influenced on electrical properties of conductive MW-CNTs. The experimental results indicated that fucntionalization with PFPE peroxide is a suitable technique to modify and control physical-chemical properties of MW-CNTs

Electrodeposition of Hierarchical Nanostructured Gold Coatingsas Facile Route for Fabrication of Superhydrophobic Surfaces

Herein electrochemical approaches for fabrication of hierarchical nanostructured gold coatings (HNGCs) are presented. Examples of HNGCs obtained by electrodeposition in sulphite based electrolyte on nickel electroplated copper (Ni/Cu) substrates are reported. The morphology and microstructure of the nanostructured surface were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD). The effects of the electrodeposition current density (J) and deposition time on the morphological features of nanostructured gold coating will be discussed. The surface wettability on thiols treated gold surface as a function of the electrodeposition current density is investigated. Thiols treated electrodepsited HNGCs can possess superhydrophobic behavior with water contact angle of 179 °

Functionalization of multi-walled carbon nanotubes with perfluoropolyether peroxide to produce superhydrophobic properties

Multi-walled carbon nanotubes (MWCNTs) have been functionalized through perfluoropolyether (PFPE) radicals obtained by thermal decomposition of linear PFPE peroxide. The reactivity of MWCNTs with PFPE peroxide has been compared with the direct fluorination of MWCNTs using elemental fluorine in mild conditions. The experimental results indicated that the functionalization with PFPE peroxide and the direct fluorination with elemental fluorine were suitable techniques to modify and control the physical-chemical properties of MWCNTs. After the introduction of PFPE chains on the MWCNT surface, the wettability of MWCNTs changed from hydrophilic to superhydrophobic, because the low surface energy properties of PFPE were transferred to the MWCNT surface. However, the linkage of PFPE chains weakly influenced the electrical properties of conductive MWCNTs. The amount of PFPE chains linked to the carbon nanotubes, the PFPE fluids obtained by homocoupling side-reactions and the decomposed portion of PFPE have been evaluated by mass balance. The modified MWCNTs have been characterized by X-ray photoelectron spectroscopy, thermal gravimetric analysis, X-ray diffraction, scanning electron microscopy, contact angle and surface area measurements. The effects of the chemical treatment on the conductive properties of MWCNTs have been studied by resistivity measurements at different applied pressures