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Abstract  

A theory of the evaluation of kinetic parameters of induction periods for non-isothermal processes is outlined and a method to obtain the parameters from non-isothermal differential scanning calorimetry measurements, based on the dependence of onset temperature of oxidation peak on heating rate, is presented. The applicability of the method is demonstrated on the study of oxidation induction periods of edible oils and polyolefines. In all cases, the parameters of an Arrhenius-like equation describing the temperature dependence of induction period have been obtained. It is shown that the method gives the parameters not affected by oxygen diffusion which are transferable to be used in modelling the non-isothermal induction periods where the effects of diffusion, heat transfer and evolution of reaction heat are explicitly involved. A method of estimating the residual stability after a thermooxidative stress of the material is suggested.

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Abstract  

Thermal properties such as melting and crystallization are important aspects in understanding the morphology and its contribution to the physical properties of semicrystalline polymers, such as polypropylene. The inclusion of fillers, which are small particles dispersed in the continuous polymer phase, often complicates the predictability of these properties by acting as nucleating agents or defect origins. This paper discusses the creation and use of empirical models based on experimental data for predicting and optimizing the thermal properties of agricultural filler-polypropylene (AgFiller-PP) composites, including peak melting temperature (T m), peak crystallization temperature (T c) and percent of crystallinity (X c). Experiments were performed using differential scanning calorimetry (DSC) to gather data necessary for building appropriate prediction models. Finally, additional experiments were carried out to test the prediction results generated by the models.

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Abstract  

The rate of thermal exchange reactions between carboxyl groups and14CO2 increases in the presence of catalytic amounts of alkali malonates. This catalytic effect can be utilized for preparative purposes also in the synthesis of11C-labelled aliphatic carboxylic acids from11CO2.

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The effects of the experimental conditions (sample size, heating rate, static and dynamic atmosphere) were studied on the value of the flash-ignition temperature (T i) obtained with a modified derivatograph able to measureT i simultaneously with the TG, DTG, DTA and T curves. The effects of various parameters are discussed and the optimum conditions determined.T i for bleached cotton fibre was found to be 270±1 °C.

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The glass transition of an irradiated, ultra-high molecular weight, linear polyethylene was investigated by means of the Perkin-Elmer DSC-2 differential scanning calorimeter. The experimental specific heat data were compared with those of the nonirradiated sample, obtained by DSC and adiabatic calorimetry.

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Edible wheat gluten (WG) protein films

Preparation, thermal, mechanical and spectral properties

Journal of Thermal Analysis and Calorimetry
Authors:
S. C. Mojumdar
,
C. Moresoli
,
L. C. Simon
, and
R. L. Legge

Abstract

Commercial wheat gluten (WG) films, hard wheat gluten films and soft wheat gluten films, plasticized with glycerol have been cast from water–ethanol solutions. The effect of aging on various film properties has been investigated. The films were aged for about 6 months at 50% relative humidity and ~25 °C, and the mechanical (tensile strength and the percentage of elongation at break (E b)), thermal (TG and DSC) and Attenuated Total Reflectance (ATR)-FTIR spectral properties have been studied. Changes in the protein structure were determined by ATR-FTIR spectroscopy. Films from soft WG exhibited the highest E b (508%) and the highest TS (6.33 MPa). The TG analysis results show that the moisture content in all three kinds of WG protein films is about 5%. The absence of the glycerol phase transition in DSC curves implies that there is no separate phase containing glycerol in the WG protein-glycerol films with 40% glycerol.

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Abstract  

Pentaerythritol tetranitrate (PETN) powders are used to initiate other explosives. During long-term storage, changes in powder properties can cause changes in the initiation performance. Changes in the morphology and surface area of aging powders are observed due to sublimation and growth of PETN crystals through coarsening mechanisms, (e.g. Ostwald ripening, sintering, etc.). In order to alleviate the sublimation of PETN crystals under service conditions, stabilization methods such as thermal cycling and doping with certain impurities during or after the crystallization of PETN have been proposed. In this report we present our work on the effect of impurities on the morphology and activation energy of the PETN crystals. The pure and impurity doped crystals of PETN were grown from supersaturated acetone solution by solvent evaporation technique at room temperature. The difference in the morphology of the impurity-doped PETN crystal compared to pure crystal was examined by optical microscopy. The changes in the activation energies and the evaporation rates are determined by thermogravimetry (TG). Our activation energies of evaporation agree with earlier reported enthalpies of vaporization. The morphology and activation energy of PETN crystals doped with Ca, Na, and Fe cations are similar to that for pure PETN crystal, whereas the Zn-ion-doped PETN crystals have different morphology and decreased activation energy.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
N. Alberro Macias
,
I. Pupo González
,
L. Valcárcel Rojas
,
D. Frías Fonseca
,
J. R. Estévez Álvarez
,
D. López Sánchez
,
A. Montero Álvarez
,
D. Simón Pérez
,
M. A. Isaac Tejera
, and
J. F. Pérez Oliva

Summary  

The quality of the potable and purified for haemodialysis waters used in the National Institute of Nephrology was evaluated since 2002 up to now. A total of 20 chemical components were analyzed. The analytical results were compared with the admissible maximum concentrations according to the Cuban Standard NC 92-02:85 for potable water and with the Spanish Standard UNE 111-301-90, related to the quality of water for use in haemodialysis. The quality of both types of water was found to comply with the Standards regulations. The CEADEN analytical chemistry laboratory operates a quality management system since 1992, that was credited according to ISO/IEC 17025 requirements.

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