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Abstract  

The numerical simulation of the temperature and relative crystallinity developed across the thickness of a poly(3-hydroxybutyrate-co-11 mass%3-hydroxyvaleate) (PHBV) part upon cooling from the melt as a function of the temperature of the cooling fluid (water) is presented. A modified form of the Avrami equation was used to predict the crystallinity as a function of the temperature. A simple expression was used to relate the kinetic constant k with the temperatures. Temperature profiles were predicted by coupling the above mentioned equations to the one-dimensional unsteady-state thermal energy equation through a heat term describing the crystallization heat. Cooling temperatures were in the range between 20 to 80°C and were restricted by the glass transition temperature of the material and the degree of under-cooling, respectively. Even degrees of crystallinity were predicted for part- thicknesses lower than 10 mm cooled at 60°C, while a fluid temperature of 40°C was more appropriate for a 20 mm - thick part. The model predicted uneven crystallinity profiles for part-thicknesses higher than 30 mm.

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Nanocomposites based on gelatin and montmorillonite

Morphological and thermal studies

Journal of Thermal Analysis and Calorimetry
Authors:
J. Martucci
,
A. Vázquez
, and
R. Ruseckaite

Abstract  

Model gelatin/montmorillonite (Ge/MMt) composites were obtained for a variety of unmodified clay concentrations and in the absence of additives, with the main goal of evaluating the effect of the morphologies developed on the composites thermal stability. Morphologies turned form partially exfoliated to exfoliate/intercalated and eventually agglomerated with increasing clay loading, as was observed by atomic force microscopy. Formulations containing 3–10 mass% montmorillonite resulted in an enhancement of composites thermal stability due to stabilizing interactions between co-components, such as strong hydrogen-type bonds, in agreement with the partially exfoliated/intercalated morphologies. Higher clay concentrations showed lower stabilizing effect in agreement with the agglomerated structures developed and the less effective interactions between co-components.

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Abstract  

Thermal analysis of jute fibre reinforced vinylester resin with 30 vol% of fibre were performed by TG/DTG under dynamic conditions. The fibres were treated with alkaline solution at different temperatures and the final composition (cellulose, hemicellulose and lignin) of the fibre was determined by chemical analysis. Apparent activation energies were determined using a variety of conventional thermogravimetric methods. Two peaks were found in the composite differential curves: the first peak close to 327 and the second peak at 408°C. The apparent activation energy values for the second peak decreased when fibre were treated. The addition of the jute fibres produced a slightly decrease in the thermal stability of the composites.

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Abstract  

The isothermal crystallization behavior of layered silicate/starch-polycaprolactone blend nanocomposites was studied by means of differential scanning calorimetry (DSC) measurements. The theoretical melting point was higher for the matrix than for nanocomposites. At low clay concentration, the induction time decreased and the overall crystallization rate increased acting as nucleating agent whereas at higher concentrations became retardants. Classical Avrami equation was used to analyze the crystallization kinetic of these materials. n values suggested that clay not only affected the crystallization rate but also influenced the mechanism of crystals growth. An Arrhenius type equation was used for the rate constant (k). Models correctly reproduced the experimental data.

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Abstract  

Non-isothermal crystallization of MaterBi-Z (starch-polycaprolactone blend) and its nanocomposites with different clay contents (0, 2.5 and 5 mass%) was studied. The experimental data show that clay can be act both as nucleating or retarding agent depend on the clay content. Kinetic parameters obtained by using a non-linear regression method, i.e., Kamal’s model and Dietz’s modification, were able to describe the non-isothermal crystallization behavior of the studied materials. A full model that takes into account the induction and growth of the crystal during cooling under non-isothermal conditions was used to obtain a continuous cooling transformation diagrams.

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Abstract  

A stack of natural samarium was bombarded with 87 MeV -particles. Cumulative cross sections for the production of145Eu,146Eu,147Eu,148Eu,150Eu,152Eu and154Eu have been studied using gamma-ray spectroscopy. The data are compared with the theoretical results provided by equilibrium and pre-equilibrium reaction models, for this purpose we used the code ALICE of Blann.

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Investigation of RuO2-IrO2-SnO2 thin film evolution

A thermoanalytical and spectroscopic study

Journal of Thermal Analysis and Calorimetry
Authors:
Elizabet Horváth
,
J. Kristóf
,
L. Vázquez-Gómez
,
Á. Rédey
, and
V. Vágvölgyi

Abstract  

The thermal evolution process of RuO2–IrO2–SnO2 mixed oxide thin films of varying noble metal contents has been investigated under in situ conditions by thermogravimetry-mass spectrometry (TG-MS), infrared emission spectroscopy (IR) and cyclic voltammetry (CV). The gel-like films prepared from aqueous solutions of the precursor compounds RuOHCl3, H2IrCl6 and Sn(OH)2(CH3COO)2–xClx on titanium metal support were heated in an atmosphere containing 20% O2 and 80% Ar up to 600C. Chlorine evolution takes place in a single step between 320 and 500C accompanied with the decomposition of the acetate ligand. The decomposition of surface species formed like carbonyls, carboxylates and carbonates occurs in two stages between 200 and 500C. The temperature of chlorine evolution and that of the final film formation increases with the increase of the iridium content in the films. The anodic peak charge shows a maximum value at 18% iridium content.

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Journal of Thermal Analysis and Calorimetry
Authors:
M. López
,
M. Blanco
,
A. Vazquez
,
J. Ramos
,
A. Arbelaiz
,
N. Gabilondo
,
J. Echeverría
, and
I. Mondragon

Abstract  

The curing kinetics of nanocomposites based on phenolic resol cured with triethylamine (TEA) containing different amounts of organic montmorillonite was analyzed by differential scanning calorimetry. Kissinger-Akahira-Sunose (KAS) model-free kinetics has been applied to correlate the dynamic cure behaviour in the presence of modified montmorillonite. The effect in the curing of the use of different clay modifiers has also been studied. A commercial clay with hydroxyl groups (Cloisite 30B) and a customized montmorillonite (PheMMT) whose reactive groups induce condensation reactions with the resol matrix have been used. Strong dependency of activation energy on apparent conversion has been observed for all compounds.

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Journal of Thermal Analysis and Calorimetry
Authors:
J. Galán
,
J. Del Castillo
,
A. González-Pérez
,
V. Fuentes-Vázquez
, and
J. Rodríguez

Abstract  

The specific conductivities of dodecylpyridinium chloride have been determinated in water-butanol/pentanol/hexanol solutions in the temperature range of 10 to 35C, and butanol, pentanol and hexanol concentrations up to 0.05 mol kg–1. From these data the temperature dependence of the critical micelle concentration, (cmc), was determined. The molar fraction of alcohol in the micelle was estimated using the theory suggested by Motomura et al. for surfactant binary mixtures. The standard Gibbs free energy of solubilization of alcohols in the micelles was worked out using the phase separation model.

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