Search Results
Abstract
Samples of paint (P), reused PET (PET-R) and paint/PET-R mixtures (PPET-R) were evaluated using DSC to verify their physical-chemical properties and thermal behavior. Films from paints and PPET-R are visually similar. It was possible to establish that the maximum amount of PET-R that can be added to paint without significantly altering its filming properties is 2%. The cure process (80–203°C) was identified through DSC curves. The kinetic parameters, activation energy (E a) and Arrhenius parameters (A) for the samples containing 0.5 to 1% of PET-R, were calculated using the Flynn-Wall-Ozawa isoconversional method. It was observed that for greater amounts of PET-R added, there is a decrease in the E a values for the cure process. A Kinetic compensation effect (KCE), represented by the equation InA=−2.70+0.31E a was observed for all the samples. The most suitable kinetic model to describe this cure process is the autocatalytic Šesták-Berggreen, model applied to heterogeneous systems.
Abstract
The thermal decomposition of aluminum phosphate monohydrate AlPO4·H2O-H4 was investigated in air using TG-DTG/DTA. The AlPO4·H2O-H4 decomposes in one step and final decomposition product (AlPO4) was studied by X-ray powder diffraction, FTIR and FT-Raman spectroscopy. The activation energies of dehydration reaction of AlPO4·H2O-H4 were calculated through the isoconversional methods of Ozawa and Kissinger-Akahira-Sunose (KAS), and the possible conversion functions have been estimated through the comparative methods. The activation energy calculated for the decomposition of AlPO4·H2O-H4 by different methods and techniques were found to be consistent. The kinetic model that better described the reaction of dehydration for AlPO4·H2O-H4 was the Fn model as simple n-order reaction and the corresponding function is f(α)=(1-α)2.75 and g(α)=-[1-(1-a)-1.75/(1.75)].
Abstract
The thermal behaviour of ammonium nitrate (AN) and its prills coated with limestone and dolomite powder was studied on the basis of commercial fertilizer-grade AN and six Estonian limestone and dolomite samples. Coating of AN prills was carried out on a plate granulator and a saturated solution of AN was used as a binding agent. The mass of AN prills and coating material was calculated based on the mole ratio of AN/(CaO + MgO) = 2:1. Thermal behaviour of AN and its coated prills was studied using combined TG-DTA-FTIR equipment. The experiments were carried out under dynamic heating conditions up to 900 °C at the heating rate of 10 °C min−1 and for calculation of kinetic parameters, additionally, at 2, 5 and 20 °C min−1 in a stream of dry air. A model-free kinetic analysis approach based on the differential isoconversional method of Friedman was used to calculate the kinetic parameters. The results of TG-DTA-FTIR analyses and the variation of the value of activation energy E along the reaction progress α indicate the complex character of the decomposition of neat AN as well as of the interactions occurring at thermal treatment of AN prills coated with limestone and dolomite powder.
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
The thermal decomposition of magnesium hydrogen phosphate trihydrate MgHPO4 · 3H2O was investigated in air atmosphere using TG-DTG-DTA. MgHPO4 · 3H2O decomposes in a single step and its final decomposition product (Mg2P2O7) was obtained. The activation energies of the decomposition step of MgHPO4 · 3H2O were calculated through the isoconversional methods of the Ozawa, Kissinger–Akahira–Sunose (KAS) and Iterative equation, and the possible conversion function has been estimated through the Coats and Redfern integral equation. The activation energies calculated for the decomposition reaction by different techniques and methods were found to be consistent. The better kinetic model of the decomposition reaction for MgHPO4 · 3H2O is the F 1/3 model as a simple n-order reaction of “chemical process or mechanism no-invoking equation”. The thermodynamic functions (ΔH*, ΔG* and ΔS*) of the decomposition reaction are calculated by the activated complex theory and indicate that the process is non-spontaneous without connecting with the introduction of heat.
Curing reaction of o-cresol-formaldehyde epoxy/LC epoxy(p-PEPB)/anhydride(MeTHPA)
Cure kinetics and molecular mechanism
Abstract
Abstract
3-Deoxy-D-erythro-hexos-2-ulose bis (thiosemicarbazone) (I) readily obtained from d-glucose reacts with copper acetate hydrate to give the corresponding chelate (II). The complex (II) was acetylated to give the corresponding tri-O-acetyl derivative (III). The (I), (II), and (III) were used as optically active curing agents for diglycidyl ether of bisphenol A (DGEBA)-based epoxy resin, and the cure reaction was studied by the non-isothermal DSC method. The maximum exothermic temperature (T p) of curing of DGEBA-(III) system shifted about 313 K toward lower temperature in comparison with the T p of DGEBA/(II) system. The average E a values obtained by using Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and isoconversional methods for non-isothermal curing of DGEBA-(I), DGEBA-(II), and DGEBA-(III) systems are 95.8, 135.5, and 85.8 kJ mol−1, respectively. The higher reactivity of (III) toward epoxide groups can be due to better solubility of the (III) in DGEBA as a result of acetylation of hydroxyl groups.
Studies on energetic compounds
Part 40. Kinetics of thermal decomposition of some bis(propylenediamine)metal perchlorate complexes
Bis(propylenediamine)metal perchlorate (BPMP) complexes like [M(pn)2](ClO4)2 (where M=Cr, Mn, Ni, Cu, Zn and pn=propylenediamine) have been prepared and characterized by gravimetric methods, infrared and elemental analysis. Thermal properties have been studied using simultaneous thermogravimetry-differential thermal analysis in atmospheres of nitrogen and air to examine the effect of atmospheric change on thermal decomposition of these complexes. Changing of the atmosphere does not cause any measurable changes in the decomposition of complexes. However, as indicated by thermoanalytical techniques, the thermal stability of present complexes decreases in the order: [Cr(pn)2](ClO4)2>[Mn(pn)2](ClO4)2>[Zn(pn)2](ClO4)2>[Ni(pn)2](ClO4)2>[Cu(pn)2](ClO4)2. Isothermal thermogravimetry, over the temperature range of decomposition has been done for all the complexes. An analysis of the kinetics of thermal decomposition was made using a model fitting procedure as well as an isoconversional method, independent of any model. The results of both kinetic approaches have been discussed critically. The explosion delay (D E) was measured to investigate the trend of rapid thermal analysis.
Abstract
The nitrate complexes of copper, nickel and zinc with diethylenetriamine (dien) i.e. [Cu(dien)2](NO3)2, [Ni(dien)2](NO3)22H2O and [Zn(dien)2](NO3)2 have been prepared and characterised. Thermal studies were undertaken using TG-DTG, DSC, ignition delay (t id) and ignition temperature (IT) measurements. Impact sensitivity was measured using drop mass technique. The kinetic parameters for both non-isothermal and isothermal decomposition of the complexes were evaluated by employing Coats-Redfern (C-R) method and Avrami-Erofeev (A-E) equations (n=2 and 3), respectively. The kinetic analysis, using isothermal TG data, was also made on the basis of model free isoconversional method and plausible mechanistic pathways for their decomposition are proposed. Rapid process was assessed by ignition delay measurements. All these complexes were found to be insensitive towards impact of 2 kg mass hammer up to the height limit (110 cm) of the instrument used. The heat of reaction (?H) for each stage of decomposition was determined using DSC.
Abstract
The thermal behaviors of [1,1,1-trifluro-3-(2-thenoyl)-acetonato]copper(II) Cu(TTA)2 and its adducts with pyridine Cu(TTA)2(Py)2, 2,2'-bipyridine Cu(TTA)2(Bpy), quinoline Cu(TTA)2(Ql)2, and dimethyl sulfoxide Cu(TTA)2(DMS) in a nitrogen atmosphere were studied under the non-isothermal conditions by simultaneous TG-DTG-DSC technique. The results showed that the evolution of the solvent molecules generally proceeded before the release of TTA in different ways according to their structures. The Cu(TTA)2(Bpy) exhibited a unique decomposition pattern due to its distinctive structure. The dependences of activation energy on extent of reaction for all the stage of each compound were determined by using an isoconversional method, Flynn-Wall-Ozawa equation, which show E values varied with reaction progress, indicating the complexity of these decomposition reactions. In addition, the values of activation energy E for TTA molecules evolution are generally higher than that for the solvent molecules release.
