Andrea Sorrentino

Epoxy/MWCNT Composite as Temperature Sensor and Electrical Heating Element

An epoxy/carbon nanotubes (CNTs) composite material with a low concentration of multiwalled CNTs (0.5 wt%) has been shown to be applicable in a wide temperature range (up to 160°C) as heating and temperature-sensing element. It can be prepared in any type of geometry allowing a simple application to all kinds of surfaces that have to be sensed and heated. The composite material itself and the electric contacts have demonstrated excellent stability even under extreme ambient conditions. The electrical resistivity of the composite has shown a temperature dependence consistent with the fluctuation-induced tunneling model. This model assumes that the electrical resistance of the nanotube network is dominated by the interconnections between the individual nanotubes rather than by the nanotube resistance itself.

Preparation and properties of new acid catalysts obtained by grafting alkoxides and derivatives on the most common supports note I — grafting aluminium and zirconium alkoxides and related sulphates on silica

Abstract In this paper we will show that it is possible to modify the acid properties of a surface, rich of hydroxyl groups by grafting in suitable conditions metal alkoxides, such as aluminium and zirconium alkoxide. Depending on the amount of metal alkoxide it is possible to obtain, after steaming of the surface and calcination, different coverage degree up to the monolayer. Iteration of the grafting technique gives a multilayer, completely modifying the orginal surface. Grafting aluminium and zirconium alkoxides pre-treated in homogeneous phase with pure sulphuric acid leads to catalysts with very strong acid sites on the surface. The acidic properties of the catalysts obtained by grafting aluminium and zirconium alkoxides and their sulphate derivatives on silica have been characterized by different techniques such as: potentiometric titrations, Temperature Programmed Desorption of organic bases and differential calorimetry to evaluate the density of the active sites and their strength. Prepared catalysts were proven in test reactions such as methanol dehydration and hydrocarbon isomerization and cracking. We have shown that sulphated catalysts have very strong acid sites of both the Bronsted and Lewis type, able to promote hydrocarbon isomerization and cracking at the relatively low temperature of 250°C.

Mechanical milling as a technology to produce structural and functional bio-nanocomposites

“Solid state mixing”, such as mechanical milling (MM), represents an ecological and economical alternative to achieve homogeneous dispersion of nano-fillers into biodegradable polymers. The advantage of working at low temperatures, without a solvent and with almost any type of polymer matrix, opens new and unexplored routes for the preparation of advanced functional materials. The use of mechanical milling contains within itself several advantages, including a strong reduction of environmental disposal, the control of the degradation processes associated with high temperature, the compatibilization of immiscible blends and the treatment of waste disposal and recycled materials. The simultaneous formation and dispersion of nanoparticles, the promotion of mechano-chemical reactions and the proper manipulation of thermo-sensitive active molecules such as antimicrobials, oxygen scavengers and antibiotics are other advantages of this process. The aim of the current work is to review the recent literature on the use of MM as a green technique to produce bio-nanocomposites. It is demonstrated how this technology could be considered an interesting option for the fabrication of novel nanostructured materials from environmental friendly resources.

Double bond oxidative cleavage of monoenic fatty chains

Abstract A two steps process for the production of azelaic acid and pelargonic acid or alternatively of ω-hydroxynonanoic and pelargonic acid, starting from respectively oleic acid and oleyl alcohol has been studied. In the first step, the monoenic reagent reacts with hydrogen peroxide, in the presence of pertungstic acid, as catalyst, to give the corresponding diol (hydroxylation of the double bond). In the second step, the reaction mixture obtained in the first step containing the formed diol and the exhausted catalyst, was additioned of cobalt acetate and reacted with molecular oxygen (oxidative cleavage of vicinal diols). As the first step has largely been studied in the literature, the study of the nature of the catalytic site and of the catalytic mechanism of the second step of the process is the main subject of this work with the objective of identifying, for this step, an independent and reusable catalyst. In particular, we focused our attention on the diol deriving from oleyl alcohol, because reagents and products are more easily separated and analyzed. The study of the mentioned reactions is complicated by the presence of respectively two or three phases in the reactor. The “in-situ” formed catalyst, active in the second reaction step, seems to be a lacunary poly-oxometalate in which cobalt, sequestered by the tungstate anion groups and accessible to the reagent, is the active component. This has been shown by polarographic analyses of the catalyst solution before and after the reaction, and is also confirmed by the observation that cobalt, sequestered by EDTA, in the absence of tungstic acid is active, too.

Performances of V2O5-based catalysts obtained by grafting vanadyl tri-isopropoxide on TiO2-SiO2 in SCR

Abstract A V2O5-based catalyst obtained by grafting vanadyl tri-isopropoxide on a TiO2-SiO2 support obtained by grafting titanium alkoxide on silica has been studied as to the selective catalytic reduction (SCR) of NO with ammonia. The performances obtained have been compared with those of other catalysts in which V2O5 was supported, respectively, on the same support by impregnating it with ammonium vanadate and on TiO2 both by grafting vanadyl tri-isopropoxide and by impregnating it with ammonium vanadate. The first mentioned catalyst turned out to be the best as to activities and selectivities. All the used catalysts and supports have been characterised using many techniques in order to explain the different performances observed. As it will be seen, activities and selectivities, in the mentioned reaction, are mainly affected by three factors that are: (i) V2O5 dispersion largely favoured by the grafting technique; (ii) the morphological properties of TiO2 surfaces that cannot be foreseen but only investigated when TiO2 is obtained by grafting titanium alkoxide on the surface of another oxide and (iii) the type of surface acidity, retaining ammonia reagent.

Oxidative dehydrogenation of ethanol to acetaldehyde on V2O5/TiO2-SiO2 catalysts obtained by grafting vanadium and titanium alkoxides on silica

Abstract Oxidative dehydrogenation of ethanol to acetaldehyde has been performed on vanadium based catalysts prepared by grafting on titania–silica supports with different procedures. A comparison of the performances of the prepared catalysts in terms of activity and selectivity has been made. Grafting technique gives place to well dispersed catalysts that resulted more selective than catalysts prepared by impregnation. In particular, very selective catalysts have been obtained by grafting vanadium–titanium bimetallic alkoxides directly on silica support. The effect of both the preparation methods and the used supports on the catalytic performances have been studied and an attempt to correlate the observed properties with the obtained results has been made.

Oxidative dehydrogenation of propane using V2O5/TiO2/SiO2 catalysts prepared by grafting titanium and vanadium alkoxides on silica

Abstract The oxidative dehydrogenation (ODH) of propane have been studied on three different vanadium oxide catalysts, containing comparable amounts of vanadium. All the proven catalysts have been prepared by grafting but following different procedures. One has been prepared by grafting vanadyl tri-isopropoxide, dissolved in n -hexane on a support of silica coated with a multi-layer of TiO 2 . The support has been prepared by grafting in three different steps titanium alkoxide on silica. Another catalyst has been prepared by partially hydrolysing vanadyl tri-isopropoxide, dissolved in isopropanol, before grafting the obtained product on the same support. The third catalyst has been prepared by reacting partially hydrolysed vanadyl tri-isopropoxide with titanium alkoxide in isopropanol and anchoring then the reaction product, a vanadium–titanium bimetallic alkoxide, directly on silica. The first and second catalysts have similar activities and selectivities, while the third catalyst is less active but more selective than the other two ones. A kinetic approach has been made and a pseudo-first order kinetic law has been used to interpret the results. All the observed catalytic phenomena have been interpreted also with the aid of the several used characterisation techniques.

Molecular orientation and strain in injection moulding of thermoplastics

Obtaining reliable predictions for molecular orientation is currently one of most challenging targets in the simulation of the injection moulding process, being the starting point toward a better understanding of how crystallisation kinetics and final morphology are influenced by flow fields during processing. Although pressure and velocity distribution can be satisfactorily described by viscous models, the viscoelastic nature of the polymer needs to be accounted for in the description of molecular orientation evolution. In this work, different choices for the dumbbell model are adopted to describe the evolution of molecular orientation by effect of kinematics obtained by a viscous approach. Comparison with literature data of birefringence distributions in injection moulded disks identifies one of the choices which correctly describes main features of data.

Determination of the effect of pressure on viscosity of an isotactic polypropylene

Despite the importance of the effect of pressure on the flow properties of a polymeric material, it is often overlooked also because of the difficulties involved in the experimental measurements. In this study, the effect of pressure on viscosity for an isotactic polypropylene was characterized in both a direct and an indirect method. In particular, a homemade device was adopted to obtain data of viscosity under high pressure and high shear rates. In addition, an indirect method based on the Simha–Somcynsky equation of state was adopted to obtain the dependence of free volume on temperature and pressure on the basis of experimental specific volume measurements; the Doolittle equation was then applied to verify the dependence of viscosity on free volume. The two methods provided similar results, confirming that, at least for polypropylene, the indirect method based on specific volume measurements can be used instead of the more complex direct measurement of the viscosity under pressure.

Fast mold surface temperature evolution: relevance of asymmetric surface heating for morphology of iPP molded samples

It is widely accepted that mold temperature has a strong effect on the amount of molecular orientation and morphology developed in a non-isothermal flowing melt. In this work, this effect was investigated in fast and asymmetric thermal conditions. Therefore, a well-characterized isotactic polypropylene was injected in a rectangular mold cavity conditioned by a purpose developed thin electric heater. Temperature evolution on the mold surface influences the cooling rates near the surface that, in turn, reduces flow stresses and facilitates molecular relaxation. Moreover, asymmetrical thermal conditions have a strong influence on the melt flow field by changing its distribution along the cavity thickness. As a consequence, the morphology distribution of the molded samples was asymmetric and showed complex and peculiar features. It was accurately characterized by optical microscopy and FESEM analysis and compared with the orientation distribution obtained by birefringence measurements.