Ferrocene and Ferrocenium Modified Clays and Their Styrene and EVA Composites

In this work, ferrocene- and ferrocenium-containing salts were employed to modify montmorillonite. X-ray measurements show an increase in the interlayer spacing upon clay modification, which means that the larger and more organophilic cations were inserted into the gallery space of montmorillonite. Attempts to prepare nanocomposites of polystyrene and ethylene vinyl acetate copolymers lead to immiscible systems; the morphology of these systems was elucidated with TEM, XRD and cone calorimetry. The thermal stability of the composites is greater than that of the virgin polymer

Comparative Study on the Flammability of Polyethylene Modified with Commercial Fire Retardants and a Zinc Aluminum Oleate Layered Double Hydroxide

Polyethylene (PE) was modified by the addition of a layered hydroxide of zinc aluminum oleate (ZnAl) and/or commercial fire retardants. Commercial additives included: melamine polyphosphate (MPP), ammonium polyphosphate (APP), triphenol phosphate (TPP), resorcinol diphosphate (RDP), decabromophenyl oxide (DECA) and antimony oxide (AO). The thermal stability and the combustion behaviors of the new composite polymeric materials are evaluated in TGA experiments and cone calorimetry. At 20% total additive loading, APP and LDH enhance the thermal stability of the PE composites and favor char formation. ZnAl leads to the best reduction in the peak of heat release rate (PHRR), 72%, while the combinations of PE with other additives give reductions in the range 20-40%. The combination of DECA and AO effectively increases the time to ignition and time to PHRR while LDH lowers these two Phosphate fire retardants parameters. APP and MPP on the other hand, do not affect the time to ignition, but they effectively increase the time to PHRR relative to the pristine polymer

Structure - property relationships of new polystyrene nanocomposites prepared from initiator-containing layered double hydroxides of zinc aluminum and magnesium aluminum

Polystyrene/layered double hydroxides (PS/LDHs) nanocomposites were prepared by free radical polymerization of styrene monomer in the presence of LDHs intercalated with 4,4′-azobis(4-cyanopentanoate) anions (LDH–ACPA). XRD and ATR-IR are used to confirm that the materials produced are layered and the presence of the azo-initiator anions in these LDHs. These LDHs were used successfully to polymerize styrene and both XRD and TEM images of the composites support the formation of a mixed exfoliated-intercalated nanocomposite for ZnAl–ACPA but a microcomposite for MgAl–ACPA. The magnesium-containing LDHs decreased the glass transition temperature (Tg) of the composites while ZnAl–ACPA did not affect Tg significantly. The Tg depression is related to enhanced polymer dynamics due to the extra free volume at the LDH additive-polymer interface. A reduction in the onset of thermal decomposition temperature was observed in PS/LDH compared to neat PS, likely due to the early decomposition of the LDH. The fire performance, as evaluated by the cone calorimeter, reveal that PS–ZnAl–ACPA shows enhanced fire properties compared to PS–MgAl–ACPA

Fostering Creativity in Higher Education Institutions: A Consulting Model

This project presents a consulting model to approach higher education institutions for the design, development, and implementation curricula, programs and academic resources about teaching creativity, teaching creatively and creative learning. This project also presents a portfolio of products and services for the consulting model. In spite of the valuable theoretical developments on how to improve education through creativity, there is still a lack of implantation of those theories. There is an opportunity is to bring creativity knowledge and training to higher education institutions through creative educational approaches. This project aims to implement educational and creativity theories into educational environments

The Role of the Trivalent metal in an LDH: Synthesis, Characterization and Fire Properties of Thermally Stable PMMA/LDH Systems

Two layered double hydroxides (LDHs), calcium aluminum undecenoate (Ca3Al) and calcium iron undecenoate (Ca3Fe), have been prepared by the co-precipitation method. XRD analysis of these LDHs reveals that they are layered materials and FT-IR and TGA confirmed the presence of the undecenoate anions in the material produced. The PMMA composites were prepared by bulk polymerization and the samples were characterized by XRD, TEM, TGA and cone calorimetry. Both additives greatly enhance the thermal stability of PMMA, while the calcium aluminum LDH gives better results when the fire properties were examined using the cone calorimeter

Aluminum-containing Layered Double Hydroxides: the Thermal, Mechanical, and Fire Properties of (Nano)composites of Poly(methyl Methacrylate)

Hydrotalcite-like anionic clays or layered double hydroxides (LDHs) of the general formula, [MII1-xMIIIx(OH)2]intra[(CH2=CH(CH2)8COO-)x•nH2O]inter, with MIII = Al and MII = Co, Ni, Cu, and Zn, have been prepared by the co-precipitation method and used to prepare nanocomposites with poly(methyl methacrylate) (PMMA). One goal of this work was to compare the morphology, thermal, fire and mechanical properties with those of the well known PMMA–montmorillonite system. The thermal properties of these systems are greatly improved relative to the virgin PMMA, with ZnAl2 and CoAl2 being the best systems when 50% mass loss is the point of comparison. NiAl2, on the other hand, is more thermally stable when 10% mass loss was the point of comparison. The mechanical properties, such as Young’s Modulus and elongation, were not significantly impacted by nanocomposite formation. The cone calorimetric results showed that the PMMA–CoAl2 system gives the best reduction (41%) in peak heat release rate (PHRR); this value is significantly larger than that seen for the PMMA–montmorillonite system. Small improvements were observed for the nickel-containing LDH with the same polymer. XRD of the char produced in the cone calorimeter, and after heating to 1000 °C, suggest the formation of a mixture of the spinel and the MII oxide for Zn, Cu and Ni systems while only the spinel was identified in the case of PMMA–CoAl2 systems

The Effects of Intralayer Metal Composition of Layered Double Hydroxides on Glass Transition, Dispersion, Thermal and Fire Properties of Their PMMA Nanocomposites

A series of aluminum-containing layered double hydroxides (LDHs), containing Mg, Ca, Co, Ni, Cu and Zn as the divalent metals, have been prepared by the co-precipitation method and used to prepare nanocomposites of PMMA by in situ bulk polymerization. The additives were characterized by Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy (XRD) and thermogravimetric analysis while the polymer composites were characterized by XRD, transmission electron microscopy, differential scanning calorimetry and cone calorimetry. Polymerization of methyl methacrylate in the presence of these undecenoate LDHs results in composites with enhanced thermal stability. The glass transition temperatures of the composites and the pristine polymers are found to be around 110 °C; this suggests that the presence of these additives has little effect on the polymer. It is found that the additive composition and the dispersion state of LDHs agglomerates in the polymer matrix influence the fire properties of composites as measured by cone calorimetry

Underpricing of venture backed IPOs: a meta-analysis approach

Listing firms are subject to underpricing mainly because of asymmetries of information, but IPOs backed by a venture capitalist are generally found to be subject to less underpricing. Although this condition is commonly verified by the empirical evidence, a consistent number of studies finds contrasting results. This paper aims to answer to the question: do venture capitalists effectively reduce underpricing at IPO? Evidence provides a negative answer, with venture-backed IPOs having higher underpricing especially in US markets. Meta-regression results confirm the different effect of VC between US and European IPOs. Results overall suggest that other explanations on underpricing might hold in US markets

Homo sapiens in the Americas. Overview of the earliest human expansion in the new world

Although it is widely recognised that America was the last continent to be populated by our species, researchers' views on various aspects of this process (e.g. the period in which it occurred, the area from which the colonizing populations came, the number of dispersal waves and the routes taken by these migrations) differ significantly. In this paper, we review both classical data and more recent findings from various research fields - including geology, paleoecology, archaeology, skeletal biology, and genetics - that may shed light on the dynamics of the colonization of the American continent, according to a critical reappraisal of the various hypotheses and models that have been advanced over time to explain this process