Layer-by-Layer Assembly of Efficient Flame Retardant Coatings Based On High Aspect Ratio Graphene Oxide and Chitosan Capable of Preventing Ignition of PU Foam

The layer-by-layer (LbL) technique is adopted for the construction of multilayers encompassing chitosan and graphene oxide (GO) platelets capable of improving the flame retardant properties open cell PU foams. The LbL assembly follows a linear growth regime as evaluated by infrared spectroscopy and yields a multilayer structure where GO platelets are embedded within a chitosan continuous matrix. 3 and 6 bi-layers (BL) can efficiently coat the complex 3D structure of the foam and substantially improve its flame retardant properties. 3BL only add 10% to the original mass and can suppress the melt dripping during flammability and reduce both the peak of heat release rate by 54% and the total smoke released by 59% in forced combustion tests. Unprecedented among other LbL assemblies employed for FR purposes, the deposition 6BL is capable of slowing down the release of combustible volatile to the limits of non-ignitability thus preventing ignition in half of the specimens during cone calorimetry tests. This has been ascribed to the formation of a protective coating where the thermally stable char produced by chitosan serves as a continuous matrix embedding GO platelets, which control volatile release while mechanically sustaining the PU foam structure

Il mare in una stanza: arte e cantieristica navale

Il saggio affronta alcune tematiche relative alla sinergia tra l’arte figurativa e la cantieristica navale, un binomio che attraversa l’intera storia delle grandi navi passeggeri impegnate sulle rotte oceaniche. In particolare vengono analizzati i motivi per cui nella decorazione di quelle navi i motivi marini sono stati per molto tempo trascurati. Dagli inizi del Novecento fino alla fine degli anni venti infatti le classi di lusso delle navi di linea erano assimilate ai grandi palazzi di rappresentanza, e come tali dovevano per quanto possibile far dimenticare i disagi dei lunghi viaggi oceanici. Il progressivo affermarsi delle tendenze funzionaliste in architettura e il fatto che le grandi navi diventeranno ideali ‘ambasciatrici’ delle rispettive industrie nazionali, farà sì che a partire dagli anni trenta gli interni dei transatlantici vengano progettati anche in funzione dell’ambiente circostante, aprendo sempre più verso l’esterno gli spazi comuni anche con l’inserimento di decori che richiamassero il mare e il viaggio. In questo campo nel secondo dopoguerra avrà un ruolo di particolare rilievo la cantieristica italiana e in particolare quella della Venezia Giulia, in grado di fornire architetti e artisti capaci di trasformare le nuove imbarcazioni in vere e proprie gallerie d’arte galleggianti

How to reduce the flammability of plastics and textiles through surface treatments: recent advances

The high flammability of plastics, polymer composites, textiles, and foams represents a severe and stringent issue that significantly limits their use in all those sectors, where resistance to a flame or an irradiative heat flux is mandatory [...

Anisotropy in nanocellular polymers promoted by the addition of needle‐like sepiolites

This work presents a new strategy for obtaining nanocellular materials with high anisotropy ratios by means of the addition of needle‐like nanoparticles. Nanocellular polymers are of great interest due to their outstanding properties, whereas anisotropic structures allow the realization of improved thermal and mechanical properties in certain directions. Nanocomposites based on poly(methyl methacrylate) (PMMA) with nanometric sepiolites are generated by extrusion. From the extruded filaments, cellular materials are produced using a two‐step gas dissolution foaming method. The effect of adding various types and contents of sepiolites is investigated. As a result of the extrusion process, the needle‐like sepiolites are aligned in the machine direction in the solid nanocomposites. Regarding the cellular materials, the addition of sepiolites allows one to obtain anisotropic nanocellular polymers with cell sizes of 150 to 420 nm and cell nucleation densities of 1013–1014 nuclei cm−3 and presenting anisotropy ratios ranging from 1.38 to 2.15, the extrusion direction being the direction of the anisotropy. To explain the appearance of anisotropy, a mechanism based on cell coalescence is proposed and discussed. In addition, it is shown that it is possible to control the anisotropy ratio of the PMMA/sepiolite nanocellular polymers by changing the amount of well‐dispersed sepiolites in the solid nanocomposites

Multicomponent bionanocomposites based on clay nanoarchitectures for electrochemical devices

Based on the unique ability of defibrillated sepiolite (SEP) to form stable and homogeneous colloidal dispersions of diverse types of nanoparticles in aqueous media under ultrasonication, multicomponent conductive nanoarchitectured materials integrating halloysite nanotubes (HNTs), graphene nanoplatelets (GNPs) and chitosan (CHI) have been developed. The resulting nanohybrid suspensions could be easily formed into films or foams, where each individual component plays a critical role in the biocomposite: HNTs act as nanocontainers for bioactive species, GNPs provide electrical conductivity (enhanced by doping with MWCNTs) and, the CHI polymer matrix introduces mechanical and membrane properties that are of key significance for the development of electrochemical devices. The resulting characteristics allow for a possible application of these active elements as integrated multicomponent materials for advanced electrochemical devices such as biosensors and enzymatic biofuel cells. This strategy can be regarded as an "a la carte" menu, where the selection of the nanocomponents exhibiting different properties will determine a functional set of predetermined utility with SEP maintaining stable colloidal dispersions of different nanoparticles and polymers in water

Fully adaptable interfacial sensors and reconstruction modeling for in situ heat transfer analysis of energy-saving materials

Adaptable interfacial sensor technologies are essential to the realization of optimized energy-saving designs through in situ monitoring the material's performance of heat transfer. Previously reported other non-invasive thermosensors can either only monitor part samplings off site or lack signal processing circuitry and sensor calibration mechanisms for accurate analysis of the thermophysical performance. Given the complexity of cutting and sampling, on-the-spot measurement and real-time reconstruction modeling of target materials are critical and requires full adaptability to ensure the accuracy of heat transfer analysis. Here we present a fully adaptable interfacial (that is, no cutting sampling is needed) sensor for in situ heat transfer analysis, which selectively and accurately measures the key parameter reflecting the heat transfer performance, i.e., thermal conductivity, as well as reconstruction modeling based on the thermal conductivity data. Our work bridges the technological gap between signal transduction, amplification and filtering, processing in interfacial thermosensors by merging inorganic/organic-based sensors that interface with the on-the-sport material with integrated circuits consolidated on a printed circuit board for complex signal processing. This adaptably movable system is used to measure the detailed porosity-dependent thermal conductivity profile of materials engaged in energy-related applications, and to make a real-time reconstruction of heat transfer process of the on-the-spot materials. This platform enables a wide range of thermophysical monitoring and reconstruction modeling applications

A Novel Method for the Preparation of Retinoic Acid-Loaded Nanoparticles

The goal of present work was to investigate the use of bioerodible polymeric nanoparticles as carriers of retinoic acid (RA), which is known to induce differentiation of several cell lines into neurons. A novel method, named “Colloidal-Coating”, has been developed for the preparation of nanoparticles based on a copolymer of maleic anhydride and butyl vinyl ether (VAM41) loaded with RA. Nanoparticles with an average diameter size of 70 nm and good morphology were prepared. The activity of the encapsulated RA was evaluated on SK-N-SH human neuroblastoma cells, which are known to undergo inhibition of proliferation and neuronal differentiation upon treatment with RA. The activity of RA was not affected by the encapsulation and purification processes

A COMPARATIVE STUDY OF ALTERNATIVE ECONOMETRIC PACKAGES: AN APPLICATION TO ITALIAN DEPOSIT INTEREST RATES

In examining the determinants of Italian deposit interest rates, we compares alternative econometric packages for estimating panel data. We focus on bank deposits, one of the main forms Italian households use to invest their financial wealth. We survey the literature on deposit rates, with particular reference to the large number of US studies. The empirical analysis is based on more than 8,000 observations for the years 1990-1996. Bank interest rates are taken from the Central Credit Register. We consider the rates on current accounts, certificates of deposit, and total deposits. Other variables are obtained from the Banking Supervision1s statistical returns. We look at the influence on interest rates of the Herfindahl index, the number of banks in each province, the rate of growth in deposits, the custodial holdings of bonds, the ratio of banking costs to total assets.With this abundance of panel data, many different specifications have been estimated using the fixed- and random-effects models. Our purpose is to examine the caveats about numerical accuracy raised by McCullogh and Vinod, who are concerned that little attention is paid to numerical accuracy in the selection of econometric packages. We compare the numerical value of the estimates of three of the most popular econometric packages featuring built-in panel data estimation algorithms: LIMDEP, STATA, and TSP. As a numerical benchmark we used Modeleasy, a general-purpose language allowing matrix operations.The preliminary results look quite promising:1) fixed-effects algorithms are numerically the same to the available decimal places.2) random-effects algorithms yield slightly different results because of the method for computing the variance components.In addition, we compare the relative efficiency of the random-effects algorithms provided by the three packages. This is done by means of a set of suitably designed Monte Carlo experiments, varying the time span and the number of provinces taken into account.