Search Results
Abstract
The thermo-oxidative degradation of poly(vinyl alcohol) (PVA) has been investigated by TG+DTG+DTA simultaneous analysis performed in static air atmosphere, at four heating rates, namely 3, 5, 10 and 15 K min−1. TG, DTG and DTA curves showed that, in the temperature range 25–700°C, four successive processes occur. The first process consisting in the loss of physical adsorbed water is followed by three processes of thermal and/or thermo-oxidative degradations. The processing of the non-isothermal data corresponding to the second process (the first process of thermo-oxidation) was performed by using Netzsch Thermokinetics — A Software Module for Kinetic Analysis. The dependence of the activation energy evaluated by Friedman’s isoconversional method on the conversion degree shows that the investigated process is complex one. The mechanism of this process and the corresponding kinetic parameters were determined by Multivariate Non-linear Regression Program and checked for quasi-isothermal experimental data. It was pointed out that the first process of thermo-oxidation of PVA consists in three consecutive steps having Avrami-Erofeev kinetic model. The obtained results can be used for prediction of the thermal lifetime of PVA corresponding to a certain temperature of use and an endpoint criterion.
Abstract
In the case of a complex mechanism of two parallel independent reactions, peak maximum evolution methods and model-fitting methods give only a mean value of the kinetic parameters, while isoconversional methods are useful to describe the complexity of the mechanism. Isothermal and non-isothermal isoconversional methods can be used to elucidate the kinetics of the process. Nevertheless, isothermal isoconversional methods can be limited by restrictions on the temperature regions experimentally available because of duration times or detection limits.
using DSC non-isothermal data . J Therm Anal Calorim 2007 90 : 807 – 812 10.1007/s10973-007-7735-2 . 22. Budrugeac , P . Kinetic of the complex process of thermo-oxidative degradation of
interpreting the experimental findings of thermal analysis. Conclusions 1. The thermal decomposition of gallium nitrate is a complex process, which begins with the simultaneous condensation of 4 mol
and intercepts with conversion degree indicate complex processes involving more than one step. On the other hand, when curves for all three steps are compared to each other, their different shapes (Figs. 4 , 5 and 6 ) indicates a different
temperature, respectively, are depicted in Fig. 4 . In general, the interaction of coal with oxygen in studied range was confirmed as complex process [ 10 ] with continuous change in effective activation energies from ca. 70 kJ mol −1 at the beginning of
Abstract
The use of references of patent search reports as transfer indications needs a good theoretical understanding of the underlying examination procedures. On this background, different patent indicators based on sample patents and on respective references can be established and combined to a network which gives an interesting insight into the complex process of knowledge transfer from science to technology.
Abstract
Complexes of adenine, AdH, with cobalt, nickel and copper chlorides were prepared and their thermodynamic functions were determined. The complexing processes are endothermic in nature. The thermal behaviour of complexes was followed up by using TG and DTA analyses. The stoichiometry of thermal decomposition of the investigated complexes was suggested.
Abstract
The thermal degradation of a sort of polyvinyl chloride was investigated. Complex processes for polyvinyl chloride degradation were evidenced. The kinetic analysis of dehydrochlorination and of subsequent processes was carried out. A change of mechanism was detected when dehydrochlorination goes to completion. The values of non-isothermal kinetic parameters determined by various methods are in a satisfactory agreement. The obtained results allowed some clarifications concerning the thermal degradation steps.
Abstract
Complex formation of D-mannonaphto-18-crown-6-ether 1 with D- and L-phenylalanine (Phe) and their derivatives was studied using conduction and titration microcalorimetry in aqueous solution, and solvent–solvent (water–chloroform) extraction. The thermal effects accompanying the complexation process were determined, but the chiral recognition effects were very small. The chiral differentiation of amino acid was observed in the experiments of the extraction from water to chloroform phase containing chiral receptor.
