Comparative study of filler influence on polylactide photooxidation

Polylactide (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

Compact Model for Multiple Independent Gates Ambipolar Devices

The model presented is a charge-based model that assures the continuity of the current and the analytical derivability of charges to obtain the parasitic capacitances. It has been conceived to support the multiple independent gates, typical of nano-array structures, where each gate controls the charge in the channel. Charge conservation implies constant current in the different section of the multiple gate nanowire FET, making possible the development of a compact model for an arbitrary number of gates. The model has been used to describe different structures (i.e. number of gates, dimension of the single transistor and ranges of applied voltages) under static conditions and the results have been verified on Silvaco TCAD simulations. The modeling approach and the attained results for some cases of study will be presented and discusse

Crystallization kinetics of poly(lactic acid)-talc composites

The crystallization kinetics of Poly(lactic acid) / talc composites were determined over a range of 0 wt.% to 15 wt.% of talc. Talc was found to change the crystallization kinetics. The presence of talc increases the crystallization rate and this increase is related to talc concentration and to crystallization temperature. In order to understand the effect of talc and PLA crystallinity on mechanical properties, dynamic mechanical thermal analyses were performed on Poly(lactic acid) / talc composites before and after an annealing process. It was demonstrated that the presence of crystals improves thermo-mechanical properties but in order to achieve good results at high temperatures the reinforcing effect of a filler such as talc is necessar

Estimating a Risky Term Structure of Uruguayan Sovereign Bonds.

Based on a joint three – factor a¢ ne model, we estimate the term structure of interest rates and default spreads for Uruguay using the reduced - form approach developed by Du¢ e and Singleton. We …nd that Uruguayan average term structure was negatively sloped between 1997 and 2003, as indicated by previous empirical evidence for low –quality debtors. Surprisingly, Uruguayan average yield curve was also negatively sloped between 1997 and 2001, when the country’s foreign –currency denominated debt was considered investment grade by the leading rating agencies. We also …nd that the estimated Uruguayan default spread is able to capture the behavior and dynamics of a more traditional country risk benchmark such as the “Uruguayan Bond Index” (UBI), with observations on a single Uruguayan bond. Finally, we …nd that regional, international and local …nancial crises cause parallel shifts in the Uruguayan yield curve, with higher increases in short –term rates, and that the banking and debt crises experienced by the country in 2002 had the biggest e¤ects on the average Uruguayan term structure.default risk; term structure; reduced-form model; default spread

ToPoliNano: Nano-magnet Logic Circuits Design and Simulation

Among the emerging technologies Field-Coupled devices like Quantum dot Cellular Automata are particularly interesting. Of all the practical implementations of this principle NanoMagnet Logic shows many important features, such as a very low power consumption and the feasibility with up-to- date technology. However, its working principle, based on the interaction among neighbor cells, is quite different with respect to CMOS devices behavior. Dedicated design and simulation tools for this technology are necessary to further study this technology, but at the moment there are no such tools available in the scientific scenario. We present here ToPoliNano, a software developed as a design and simulation tool for NanoMagnet Logic, that can be easily adapted to many others emerging technologies, particularly to any kind of Field-Coupled devices. ToPoliNano allows to design circuits following a top-down approach similar to the one used in CMOS and to simulate them using a switch model specifically targeted for high complexity circuits. This tool greatly enhances the ability to analyze, explore and improve the design of Field- Coupled circuit

MWNT Surface Self-Assembling in Fire Retardant Polyethylene-Carbon nanotubes nanocomposites

Multiwall carbon nanotubes (MWNT) were melt blended at different concentration with linear low density polyethylene (LLDPE). The nanotubes impart the fire-retardant characteristics to the polymer by formation of a thin protective film of MWNT/carbon char generated on the surface of the nanocomposites. The film formation mechanism is discusse

FDM Printability of PLA Based-Materials: The Key Role of the Rheological Behavior

Fused deposition modeling (FDM) is one of the most commonly used commercial technologies of materials extrusion-based additive manufacturing (AM), used for obtaining 3D-printed parts using thermoplastic polymers. Notwithstanding the great variety of applications for FDM-printed objects, the choice of materials suitable for processing using AM technology is still limited, likely due to the lack of rapid screening procedures allowing for an efficient selection of processable polymer-based formulations. In this work, the rheological behavior of several 3D-printable, commercially available poly(lactic acid)-based filaments was accurately characterized. In particular, each step of a typical FDM process was addressed, from the melt flowability through the printing nozzle, to the interlayer adhesion in the post-deposition stage, evaluating the ability of the considered materials to fulfill the criteria for successful 3D printing using FDM technology. Furthermore, the rheological features of the investigated materials were related to their composition and microstructure. Although an exhaustive and accurate evaluation of the 3D printability of thermoplastics must also consider their thermal behavior, the methodology proposed in this work aimed to offer a useful tool for designing thermoplastic-based formulations that are able to ensure an appropriate rheological performance in obtaining 3D-printed parts with the desired geometry and final properties