Authors:Banjong Boonchom, Chanaiporn Danvirutai, and Montree Thongkam
The thermal decomposition of synthetic serrabrancaite (MnPO4 · H2O) was studied in N2 atmosphere using TG-DTG-DTA. Thermal analysis results indicate that the decomposition occurs in two stages, which are assigned
to the dehydration and the reduction processes and the final product is Mn2P2O7. X-ray powder diffraction, FT-IR and FT-Raman techniques were used for identification of the solid decomposition product.
The decomposition kinetics analysis of MnPO4 · H2O was performed under non-isothermal condition through isoconversional methods of Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose
(KAS). The dependences of activation energies on the extent of conversions are observed in the dehydration and the reduction
reactions, which could be concluded the “multi-step” processes.
Authors:L. Tian, N. Ren, J. Zhang, H. Liu, S. Sun, H. Ye, and K. Wu
The two complexes of [Ln(CA)3bipy]2 (Ln = Tb and Dy; CA = cinnamate; bipy = 2,2′-bipyridine) were prepared and characterized by elemental analysis, infrared
spectra, ultraviolet spectra, thermogravimetry and differential thermogravimetry techniques. The thermal decomposition behaviors
of the two complexes under a static air atmosphere can be discussed by thermogravimetry and differential thermogravimetry
and infrared spectra techniques. The non-isothermal kinetics was investigated by using a double equal-double steps method,
the nonlinear integral isoconversional method and the Starink method. The mechanism functions of the first decomposition step
of the two complexes were determined. The thermodynamic parameters (ΔH≠, ΔG≠ and ΔS≠) and kinetic parameters (activation energy E and the pre-exponential factor A) of the two complexes were also calculated.
Authors:Zuzana Cibulková, Júlia Polovková, V. Lukeš, and E. Klein
The effect of γ-radiation
on the cis-1,4-polyisoprene in the presence
of oxygen is investigated by ATR-FTIR technique and non-isothermal DSC measurements.
FTIR measurements have shown that the formation of hydroperoxides, ketones,
alcohols and/or ethers is apparent already at lower, 20–50 kGy, doses
of γ-radiation and it increases significantly with the exposure time.
Besides, lactones, anhydrides, peresters, carboxylic acids, and esters are
formed, too. Spectral changes in the region of C=C conjugated double bonds
indicate a formation of shorter polyene structures and aromatic rings. Kinetic
parameters describing the temperature dependence of the induction period have
been obtained from DSC measurements using the isoconversional method. Residual
stabilities have been calculated in order to characterize the gamma radiation
effect on polyisoprene thermooxidative stability. Both methods proved that
doses lower than 50 kGy do not cause severe changes in polymer properties.
Authors:M. Alonso, M. Oliet, J. García, F. Rodríguez, and J. Echeverría
Kinetics of thermosetting polymers curing is difficult to study by isothermal
methods based on the differential scanning calorimetry (DSC) technique. The
difficulty is due to the low sensitivity of the equipment for total reaction
heat measurements during high temperature process. The aim of this paper is
to display the equivalence between a dynamic model, the Ozawa method, and
an isothermal isoconversional fit, which allows predicting the isothermal
behavior of the resol resins cure through dynamic runs by DSC. In this work,
lignin–phenol–formaldehyde and commercial phenol–formaldehyde
resol resins were employed. In addition, the isothermal kinetic parameters
for both resins were performed by means of transformation of the data obtained
from the dynamic Ozawa method.
Authors:T. Kaljuvee, I. Rudjak, E. Edro, and A. Trikkel
The effect of heating rate on the thermal behavior of ammonium nitrate (AN) and on the kinetic parameters of decomposition
of AN and its blends with limestone and dolomite was studied on the basis of commercial fertilizer-grade AN and several Estonian
limestone and dolomite samples. Experiments were carried out under dynamic heating conditions up to 900 °C at heating rates
of 2, 5, 10 and 20 °C min−1 in a stream of dry air using Setaram Labsys 2000 equipment. For calculation of kinetic parameters, the TG data were processed
by differential isoconversional method of Friedman. The variation of the value of activation energy E along the reaction progress α showed a complex character of decomposition of AN—interaction of AN with limestone and dolomite
additives with the formation of nitrates as well as decomposition of these nitrates at higher temperatures.
Authors:J. Morancho, A. Cadenato, X. Fernández-Francos, J. Salla, and X. Ramis
The purpose of this work is to analyse certain kinetic features related to thermoinduced and photoinduced isothermal curing
in the 25/75 mass% bis-GMA/TEGDMA system. The kinetic parameters associated with photo and thermal curing were determined and compared using an
isoconversional procedure and the kinetic model was obtained by means of a reduced master plot. In photocuring, the kinetic
results obtained by means of this phenomenological methodology were compared with those obtained on the basis of mechanistic
considerations. In this case, we estimated the propagation and termination constants associated with photocuring at different
conversions. When the phenomenological procedure is performed, the rate constant decreases slightly during the curing process
and the autoacceleration effect of the process is demonstrated in the kinetic model, which is autocatalytic. However, in the
mechanistic model, this same effect is noted through an increase in the rate constants, while it is assumed that the kinetic
model is in the order of n with n=1.
Authors:A. Santos, L. Polese, M. Crespi, and C. Ribeiro
The non-isothermal data given by TG curves for poly(3-hydroxybutyrate) (PHB) were studied in order to obtain a consistent
kinetic model that better represents the PHB thermal decomposition. Thus, data obtained from the dynamic TG curves were suitably
managed in order to obtain the Arrhenius kinetic parameter E according to the isoconversional F-W-O method. Once the E parameters is found, a suitable logA and kinetic model (f(α)) could be calculated. Hence, the kinetic triplet (E±SD, logA±SD and f(α)) obtained for the thermal decomposition of PHB under non-isothermal conditions was E=152±4 kJ mol−1, logA=14.1±0.2 s−1 for the kinetic model, and the autocatalytic model function was: f(α)=αm(1−α)n=α0.42(1−α)0.56.
The thermooxidative degradation of poly(vinyl chloride) (PVC), chlorinated polyethylene (CPE) and PVC/CPE blend 50/50 was
investigated by means of dynamic and isothermal thermogravimetric analysis in the flowing atmosphere of air. To estimate the
thermooxidative stability of the samples the characteristics of thermogravimetric (TG) curves were used. Kinetic parameters
(the apparent activation energy E and preexponential factor Z) were calculated after isoconversional method for the first
stage of dynamic degradation where dehydrochlorination (DHCl) of PVC and/or CPE is the main degradation reaction. Despite
the chemical resemblance, the degradation mechanisms of CPE and PVC are different, as a consequence of differences in microregularity
of the corresponding polymer chains. The addition of Ca/Zn carboxylates as well as the ratio of Ca and Zn carboxylates have
considerably different influence on the investigated polymers.
Authors:W. He, F. Deng, G.-X. Liao, W. Lin, Y.-Y. Jiang, and X.-G. Jian
New special engineering thermoplastics, poly(phthalazinone ether sulfone) (PPES) and poly(phthalazinone ether sulfone ketone)
(PPESK), containing phthalazinone are synthesized through step-polymerization. The kinetics of thermal degradation of PPES
and PPESK (1/1) in nitrogen is investigated at several heating rates by thermogravimetry (TG). It is concluded that, based
on using Satava’s theory, the thermal degradation mechanism of PPESK (1/1) is nucleation and growth, the order of reaction
of the degradation process is one (n = 1). In contrast, the thermal degradation mechanism of PPES is a phase boundary controlled reaction and the order of the
reaction is two (n = 2). The kinetic parameters, including reaction energy and frequency factor of thermal degradation reaction for PPES and
PPESK (1/1) are analyzed using isoconversional Friedman, Kissinger–Akahira–Sunose (K–A–S) and Ozawa method. In addition, the
study focus on the influence of heating rate and ratio of ketone/sulfone on thermal stability and the life estimation are
Authors:Luciana Guinesi, C. Ribeiro, Marisa Crespi, A. Santos, and Marisa Capela
This work aims the evaluation of the kinetic triplets
corresponding to the two successive steps of thermal decomposition of Ti(IV)–ethylenediaminetetraacetate
complex. Applying the isoconversional Wall–Flynn–Ozawa method
on the DSC curves, average activation energy: E=172.49.7
and 205.312.8 kJ mol–1, and pre-exponential
factor: logA=16.380.84 and 18.961.21
min–1 at 95% confidence interval could be
obtained, regarding the partial formation of anhydride and subsequent thermal
decomposition of uncoordinated carboxylate groups, respectively.
From E and logA values,
Dollimore and Mlek methods could be applied suggesting PT (Prout–Tompkins)
and R3 (contracting volume) as the kinetic model to the partial formation
of anhydride and thermal decomposition of the carboxylate groups, respectively.