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The effect of clay dispersion on the crystallization behavior of isotactic polypropylene (iPP)-based nanocomposites is reported. The Tm 0 of the materials was calculated by the method proposed by Marand, the kinetics of crystallization was evaluated by the Avrami analysis and also the Hoffman-Lauritzen theory of crystallization regimes was applied. Montmorillonite was found to depressTm 0, to enhance the rate of crystallization and to ease the chain folding of macromolecules. These effects were magnified if clay was exfoliated, rather than intercalated

Biodegradable polycaprolactone/organoclay nanocomposites were prepared by solvent casting, using different amounts of filler and matrices differing by average molecular weight. Intercalated nanocomposites were obtained. The nanocomposites were characterized by wide-angle X-ray diffraction (WAXD) and small-angle Xray scattering (SAXS) methods. Negligible variations in the degree of crystallinity were detected by WAXD. The thickness of crystalline lamellae, measured by SAXS, increased in low molecular weight polymer nanocomposites with increasing clay amount; this effect was weakened in matrices with high molecular weight. Differential scanning calorimetry showed an inhibiting effect of clay on crystallization. The composites' ductility was largely increased, whereas stiffness was retained. After biodegradation in compost, in all samples, the degree of crystallinity was increased, meaning that the less ordered portion of the sample was preferentially degraded. Clay slowed down the biodegradation rate, coherently with the observed increase in the lamellar thickness due to the filler. This may offer a strategy for tuning the biodegradability by calibrating their semicrystalline framework. POLYM. ENG.

In this work, an easy, quick and reproducible wet-synthesis coprecipitation route starting from oxalate precursors was optimised to synthesise cobalt, nickel, zinc and magnesium spinel ferrites CoFe2O4, NiFe2O4, ZnFe2O4 and MgFe2O4, as well as the manganese perovskite ferrite MnFeO3. Crystalline purity and crystallite sizes ranging from 30 to 190 nm were investigated by means of powder X-ray diffraction, and uniform morphology of the particles was shown through transmission electron microscopy. The chosen synthetic route afforded an excellent stoichiometric control over the products, as confirmed by combined X-ray photoelectron spectroscopy and inductively coupled plasma atomic emission spectroscopy analyses. The site geometry, degree of inversion in the spinels and chemical environments in the ferrites were explored by Mössbauer spectroscopy. The thermal evolution of the compounds during calcination and the decomposition pattern of the oxalates were studied through differential scanning calorimetry coupled with thermogravimetric analysis as well as in situ temperature-programmed X-ray diffraction. Magnetic properties of these oxides, as well as the transition of the perovskite from paramagnetic to ferrimagnetic behaviour at low temperatures, were investigated by superconducting quantum interferometer magnetometr

Polyvinyl alcohol (PVA) electrospun nanofibers containing Ag nanoparticles (NPs) have been deposited on glass substrates. The aim of the work was to test the feasibility of this approach for the detection of biogenic amines by using either the Ag localized surface plasmon resonance quenching caused by the adsorption of amines on Ag NPs or by detecting the amines by surface enhanced Raman spectroscopy (SERS) after adsorption, from the gas phase, on the metal NPs. Two different approaches have been adopted. In the first one an ethanol/water solution containing AgNO3 was used directly in the electrospinning apparatus. In this way, a simple heat treatment of the nanofibers mat was sufficient to obtain the formation of Ag NPs inside the nanofibers and a partial cross-link of PVA. In the second procedure, the Ag NPs were deposited on PVA nanofibers by using the supersonic cluster beam deposition method, so that a beam of pure Ag NPs of controlled size was obtained. Exposure of the PVA mat to the beam produced a uniform distribution of the NPs on the nanofibers surface. Ethylendiamine vapors and volatile amines released from fresh shrimp meat were chemisorbed on the nanofibers mats. A SERS spectrum characterized by a diagnostic Ag-N stretching vibration at 230 cm(-1) was obtained. The results allow to compare the two different approaches in the detection of ammines.

Nanocomposites based on poly(vinylidene fluoride) were prepared with montmorillonite by solution blending. The samples were characterized by small angle X-ray scattering, wide angle X-ray diffraction, Fourier transform infrared spectroscopy, and differential scanning calorimetry. Different crystallization conditions, that is, evaporation of the solvent and coprecipitation with two different antisolvents, H2O or supercritical CO2 (scCO2), were tested and their influence on the resulting structure and morphology of the samples were studied. Coprecipitation with scCO2 induced an ordinate crystalline framework and an intercalated morphology of clay, with a consequent large improvement in modulus

Tannins have been largely studied as wood additives and wood adhesives. In a perspective of a desirably increased utilization of natural raw material in the wood timber industries, this study provides further and specific information on the use of condensed tannins to improve the heat resistance of urea-formaldehyde (UF) resins. The results obtained by thermomechanical and thermogravimetric analyses show that high percentage (33 and 50 %) of quebracho tannin in UF-tannin blend dramatically improves the overall UF thermal resistance, but 50 % of tannin decreases the maximum value of modulus of elasticity (MOE) of the bonded joint. The best balance between mechanical performance and decreased degradation at high temperature is obtained with 33 % of quebracho tannin. The MOE value of UF + 33 % of quebracho tannin at 260 A degrees C is seven times greater than MOE of UF control. Thermograms show that quebracho tannin has a beneficial effect on increasing the resistance of glue-mix to degradation induced by temperature. When the content of tannin in the glue-mix is increased up to 50 %, the resin degrades completely at about 670 A degrees C, i.e. more than 50 A degrees C higher than neat UF resin. This improvement is related mainly to the resorcinol-type ring structure of tannin and the alkaline pH of UF + quebracho tannin glue mix that confer a higher resistance against joint degradation to UF even at elevated temperatures

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