205 research outputs found
Synthesis of talc-like filler with covalently bonded organic modifiers as novel additive for polymer nanocomposites
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Comparative study of filler influence on polylactide photooxidation
No full textPolylactide (PLA) based nanocomposites of organically modified montmorillonite and micro-talc based micro- composites were prepared with different compositions and were UV-light irradiated under artificial accelerated conditions representative of solar irradiation. The chemical modifications resulting from photo-oxidation were followed by infrared (IR) and ultraviolet (UV)-visible spectroscopies. The infrared analysis of PLA photooxidation shows the formation of a band at 1847 cm-1 due to the formation of anhydrides. The filler addition provokes an increase of anhydride formation rate dependent on filler nature, amount and dispersion degree on the matrix. The main factors that influence oxidation rate are the total extension of polymer/filler interfacial area and the presence of transition metal impurities of clays
Flammability and Thermal Stability in Clay/Polyesters Nano-Biocomposites
No full textIn these years we are witnessing the growth of the biopolymers durable application markets such as buildings, transportation, electronic equipments etc. Thus, the fire retardancy issue is becoming important and it is expected that in the next future more and more research will be devoted to the subject. So far, a limited number of papers reports on flame retardant properties of biopolyesters and they are mainly on polylactide. Most of the papers published on this topic regarding biopolyesters, concern polyesters fire retarded by traditional fire retardants developed for oil sourced polymers, especially polyesters such as polyethylene terephthalate or other polymers such as polycarbonate. The recently developed use of nanoclays to fire retard polymers has proved to be beneficial also for polyesters from renewable resources. This chapter reviews the studies published on thermal and fire behaviour of polylactide nanocomposites based on clays. Indeed, PLA is the most important commercial plastic from renewable resources (RRP) polyester for which durable applications are being developed and fire retardant aspects are investigate
Silver nanoparticle ink technology: state of the art
No full textKrishna Rajan, Ignazio Roppolo, Annalisa Chiappone, Sergio Bocchini, Denis Perrone, Alessandro Chiolerio Center for Space Human Robotics, Italian Institute of Technology, Turin, Italy Abstract: Printed electronics will bring to the consumer level great breakthroughs and unique products in the near future, shifting the usual paradigm of electronic devices and circuit boards from hard boxes and rigid sheets into flexible thin layers and bringing disposable electronics, smart tags, and so on. The most promising tool to achieve the target depends upon the availability of nanotechnology-based functional inks. A certain delay in the innovation-transfer process to the market is now being observed. Nevertheless, the most widely diffused product, settled technology, and the highest sales volumes are related to the silver nanoparticle-based ink market, representing the best example of commercial nanotechnology today. This is a compact review on synthesis routes, main properties, and practical applications. Keywords: silver nanoparticles, surface plasmon resonance, nanocomposites, inks, printed electronic
Impedance Hyperbolicity in Inkjet-Printed Graphene Nanocomposites: Tunable Capacitors for Advanced Devices
No full textAn easy method for the fabrication of a completely tunable capacitor based on inkjet-printed hybrid organic systems is here reported. The quantum relativistic properties of graphene-induce electronic resonances between the polyaniline polymeric matrix and the graphene filler, with extremely long transfer rates. These events induce peculiar physical phenomena due to impedance hyperbolicity, such as voltage-controlled phase shifting. The apparent capacitance is shown to diverge to infinity having a sign dependent on the frequency sweep direction. Hence devices may be geometrically tuned to operate with desired capacitance (either positive or negative) at the desired frequency. Among various possibilities of theoretical models that can explain the negative capacitance found, the standard space charge accumulation theory is considered and compared to other quantum relativity effects. The discussion of experimental results based on those theories suggests that a new paradigm is required for a comprehensive explanation of the observed phenomena, which include the observation of high-frequency (MHz) negative capacitance, voltage-controlled phase shifting, and diverging negative/positive capacitance in correspondence of the characteristic resonance frequency (kHz). The various possibilities of exploiting these peculiar properties in advanced electronic devices are also discussed
Method for the preparation of polyaniline/reduced graphene oxides composites
No full textThe present invention concerns a method for obtaining polyaniline/reduced graphene oxide composites comprising the steps of dispersing the graphene oxide in an acid aqueous solution containing an emulsifying agent to obtain a graphene oxide dispersion; dissolving one or more aniline oligomers in an organic solvent to obtain an oligomer solution; mixing the oligomer solution with the graphene oxide dispersion, said oligomer being added in a stoichiometric excess compared to the quantity required to complete the graphene oxide reduction; adding to the suspension of the polyaniline/reduced graphene oxide composite an oxidizing agent in a stoichiometric quantity compared to said excess of oligomer so as to oxidize the excess of said oligomer to obtain a suspension of the polyaniline/reduced graphene oxide composite
Thermomechanical improvement of glycerol plasticized maize starch with high loading of cellulose, flax and talc fillers
No full textFor the purpose of extending the applicability fields of thermoplastic starch (TPS), a study on their properties with high filler loadings was performed. Two different organic natural reinforcements (cellulose and flax) and a typical mineral filler (talc) were incorporated in TPS using melt blending. The resulting composites were observed on fragile fracture surfaces by scanning electron microscopy to study the filler/matrix adhesion. Magnifications revealed good TPS−fibre interfacial interac t ion with limited debonding. The thermomechanical properties by dynamic mechanical thermal analysis (DMTA) and the correlation with the filler amount (from 10 to 50 wt%) were thoroughly investigated at 50% relative humidity and 23°C. The tests evidenced a huge increase in composite storage moduli (E′) of more than 200% with respect to the neat matrix. Moreover, the resulting DMTA experimental data were interpolated with the Cox − Krenchel micromechanical model. To this aim, the necessary measures of the filler dimensions were calculated after the extrusion process on water-dissolved residues using an optical microscope. This model was able to correctly follow the experimental results also at high filler loadings
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