Fracture behavior and mechanical,thermal, and rheological properties of biodegradable films extruded by flat die and calender

The development of biodegradable materials for tailored applications, particularly in the field of polymeric films and sheets, is a challenging technological goal as well as a contribution to help protect the environment. Poly(lactic) acid (PLA) is a promising substitute for several oil-based polymers; however, to overcome its thermal and mechanical drawbacks, researchers have developed solutions such as blending PLA with polybutylene adipate terephthalate (PBAT), which is capable of increasing the ductility of the final material. In this study, PLA/PBAT binary blends, with minimum possible content of nonrenewable materials, were examined from processing, thermal, morphological, and rheological perspective. An optimized PLA/PBAT ratio was chosen as the polymeric basis to obtain a biodegradable formulation by adding a biobased plasticizer and appropriate fillers to produce a micrometer film with tailored flexibility and tear resistance. The processing technology involved flat-die extrusion, followed by calendering. The tearing resistance of the produced film was investigated, and the results were compared with literature data. A study on the essential work of fracture was implemented to explore the mode III out-of-plane fracture resistance starting from a trouser tear test.     

Three-pencil lattices on triangulations

In this paper, three-pencil lattices on triangulations are studied. The explicit representation of a lattice, based upon barycentric coordinates, enables us to construct lattice points in a simple and numerically stable way. Further, this representation carries over to triangulations in a natural way. The construction is based upon group action of S ₃ on triangle vertices, and it is shown that the number of degrees of freedom is equal to the number of vertices of the triangulation.      

A characterization of Denniston's maximal arcs

Our main result is the following characterization of Denniston's maximal arcs: If a maximal arcK in PG(2,q),q even, is invariant under a linear collineation group of PG(2,q) which is cyclic and has orderq+1, thenK is a Denniston's maximal arc.This work was partially supported by a grant of M.P.I. (Research project Strutture geometriche combinatorie e loro applicazioni).     

Metal Oxoclusters as Molecular Building Blocks for the Development of Nanostructured Inorganic–Organic Hybrid Thin Films

Silica-based inorganic–organic hybrid thin films embedding the organically modified oxohafnium clusters (Hf₄O₂(OMc)₁₂, OMc=OC(O)–C(CH₃)=CH₂) were obtained by photo-activated free radical copolymerisation of the methacrylate groups of the cluster with those of the pre-hydrolysed (methacryloxypropyl)trimethoxysilane (MAPTMS, (CH₂=C(CH₃)C(O)O)(CH₂)₃Si(OCH₃)₃). By this route, a covalent anchoring of the cluster to the forming silica network was achieved. Samples characterized by two different Si/Hf compositions (18:1, 5:1) were prepared. The surface and in-depth composition of the thin films were investigated through Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). XPS depth profiles performed on the thin layers evidenced a homogenous in depth distribution of the hafnium guest species within the whole silica films and sharp film-substrate interfaces. Broad band dielectric spectroscopy (BDS) measurements permitted to investigate the electric response of the obtained films in the frequency and temperature range of 40 Hz – 1 MHz and 0–160°C.     

A boxmodel development to study the relationships between the photo-oxidants and the particles formation in the troposphere

The model BAGS (Boxmodel for Aerosol and Gasphase Simulations) has been developed. It is composed of two major modules: the first one describes the system of the chemical reactions in the gaseous phase, the second one calculates the aerosol chemical composition and the dimensional distribution of the particles. The boxmodel has been developed with the introduction of new chemical and physical processes, not previously included, in particular the formation of Secondary Organic Aerosol. The other implemented processes are a module for the dynamic of the particle population, nucleation, coagulation and dry deposition. The last phase of the work has been a check of the BAGS capabilities by a series of tests, that have permitted to compare it with other models (MAPS and MADM). The tests in particular have concerned the aerosol water content prediction, the photochemistry, the condensation of the inorganic compounds and the formation of Secondary Organic Aerosol.     

A palladium-catalyzed synthetic approach to new Huperzine A analogues modified at the pyridone ring

The synthesis of two new Huperzine A analogues is reported. Both products present an amino substituted benzo-fused system in place of the pyridone ring of the natural alkaloid. The synthetic strategy to the two analogues is based on three different key palladium-catalyzed steps, namely a carbonylation reaction, an epoxide isomerization and a bicycloannulation reaction.     

Measurement of the carbonaceous component in the Milan urban particulate matter

The carbonaceous component in the Milan urban particulate matter, i.e. the two components black carbon (BC) and organic carbon (OC), has been measured by means of a thermogravimetric analyzer combined with an infrared spectrophotometer (TGA/FT-IR). While black carbon may be considered a primary pollutant, organic carbon includes both primary emissions and secondary organic aerosols. Since carbonaceous aerosol (including a small quantity of inorganic carbon, too) makes up roughly from 25% to 50% of the average annual PM 2.5 mass concentration, a deeper understanding of this component is required. The TGA/FT-IR technique, employed for the first time to our knowledge for the quantification of the particulate matter carbonaceous component, allows, thought the results here presented are preliminary, to assess the two components BC and OC in a simple way especially if compared with the methods reported in the literature. The total carbon (TC) determinations performed by TGA/FT-IR on Milan urban particulate matter are in good agreement with the results obtained by a total organic carbon (TOC) analyzer operating directly on the solid sample.     

Synthesis of low molecular weight perfluoro oxymethylene vinyl ethers

Perfluoro oxymethylene vinyl ethers have been formed by a multi-step synthesis. The key intermediates are low molecular weight perfluoropolyether (PFPE) fluoroformates CF₃O(CF₂O)_nCOF (I) n=1-6 obtained from the photo-oxidation of perfluoro propene (HFP) in perfluorohexane. Under certain conditions the light-mediated fluorination of PFPE fluoroformates (I) gives PFPE hypofluorites CF₃O(CF₂O)_nCF₂OF (II), which can be added to sym dichlorodifluoroethene to form the dichloro adduct CF₃O(CF₂O)_nCF₂OCFClCF₂Cl (III) which, after dechlorination, gives the desired vinyl ethers CF₃O(CF₂O)_nCF₂OCFCF₂ (IV). Every reaction step has to be properly controlled as far as the reaction variables are concerned. A mechanistic scheme is presented that is consistent with the observed experimental data.     

Determination of trace rare earth elements by X-ray fluorescence spectrometry after preconcentration on a new chelating resin loaded with thorin

A very stable chelating resin was prepared by adsorption of (o-[3,6-disulfo-2-hidroxy-1-naphthylazo]-benzenearsonic acid) (thorin) on a macroporous resin Amberlite XAD-7. The optimal conditions for preparing it were obtained through the study of the adsorption properties of the resin and the thermodynamic quantities of the adsorption processes. Likewise, the behavior of the loaded resin with the rare earth elements (REE) were studied (pH of retention, sorption kinetics, etc). The conditions to prepare a thin film with this system were also evaluated. The loaded resin was successfully used for the separation and preconcentration of Sm(III), Eu(III) and Gd(III) prior to their determination by X-ray fluorescence (XRF) spectrometry. The preconcentration factor obtained was 500 and the concentrations at low detection limit were 13.8, 17 and 15.7 microg l(-1) for Sm, Eu and Gd, respectively.     

Oxiranyl anion-mediated synthesis of highly enantiomerically enriched styrene oxide derivatives

[reaction: see text] The stereospecific alpha-lithiation of optically active styrene oxides and the trapping reaction of the corresponding highly reactive intermediates with electrophiles to produce optically active styrene oxide derivatives are described. This methodology has been applied to the synthesis of an optically active oral antifungal agent of industrial interest.