Kinetic parameters obtained for thermal decomposition of acrylic resins present in commercial paint emulsions

Samples of water based commercial acrylic resin paints were spread in a film form on slides, dried at room temperature and exposed to solar radiation for up to eight months.The characterization and quantification of resins and charges in the white paint emulsion were carried out for the thermal decomposition. Besides this, X-ray diffractometry was used to identify CaCO3 as charge and TiO2 (rutile phase) as pigment.It was observed through thermal techniques similar behavior to the samples even though with varied exposure time.Kinetic studies of the samples allowed to obtain the activation energy (Ea) and Arrhenius parameters (A) to the thermal decomposition of acrylic resin to three different commercial emulsion (called P-1, P-2, P-3) through non-isothermal procedures. The values of E. varied regarding the exposition time (eight months) and solar radiation from 173 to 197 U mol(-1) (P-1 sample), from 175 to 226 W mol(-1) (P-2 sample) and 206 to 197 kJ mol(-1) (P-3 sample).Kinetic Compensation Effect (KCE) observed for samples P-2 and P-3 indicate acrylic resin s present in these may be similar in nature. This aspect could be observed by a small difference in the thermal behavior of the TG curves from P I to P-2 and P-3 sample.The simulated kinetic model to all the samples was the autocatalytic estdk Berggreen.

Influence of processing conditions on the thermal decomposition of SrTiO3 precursors

The present work investigates the influence of milling and calcination atmosphere on the thermal decomposition of SrTiO3 powder precursors. Both pure and neodymium-modified SrTiO3 samples were studied. Milling did not significantly influence numerical mass loss value, but reduced the number of decomposition steps, modifying the profiles of the TG and DTA curves. on the other hand, milling increases the amount of energy liberated by the system upon combustion of organic matter. It was also observed that the milling process, associated to the calcination in an oxygen atmosphere, considerably decreases the amount of organic matter and increases the final mass loss temperature.

Photoluminescence in amorphous PLZ

Amorphous and crystalline powder of PLZ was prepared by using the polymeric precursor method. TGA-DSC (Thermal analysis and Differential Scanning Calorimetry) shows the decomposition of polymeric resin, an amorphous phase and the crystallization of powder. Raman scattering of powder shows an amorphous and semicrystalline phase at 450 and 550 degreesC, respectively. XRD (X-ray diffraction pattern) of powder shows high crystallinity at 700 degreesC/3 h. PL (Photoluminescence) analysis of powder at 300 degreesC/3 h shows a broad asymmetric peak at 585 nm and increases of calcining time led to intense peaks of PL at 300 degreesC/6 h. This emission could be attributed to Zr --> O from the oxygen-2p orbitals to the zirconate-3d orbitals. (C) 2003 Elsevier Ltd and Techna S.r.l. All rights reserved.

Sol-gel entrapped cobalt complex

This work describes optimized conditions for preparation of a cobalt complex entrapped in alumina amorphous materials in the form of powder. The hybrid materials, CoNHG, were obtained by a nonhydrolytic sol-gel route through condensation of aluminum chloride with diisopropylether in the presence of cobalt chloride. The materials were calcined at various temperatures. The presence of cobalt entrapped in the alumina matrix is confirmed by ultraviolet visible spectroscopy. The materials have been characterized by X-ray diffraction (XRD), surface area analysis, thermogravimetric analysis (TGA), differential thermal analyses (DTA) and transmission electron microscopy (TEM). The prepared alumina matrix materials are amorphous, even after heat treatment up to 750 degreesC. The XRD, TGA/DTA and TEM data support the increase of sample crystallization with increasing temperature. The specific surface area, pore size and pore diameter changed as a function of the heat treatment temperature employed. Different heat treatment temperatures result in materials with different compositions and structures, and influence their catalytic activity. The entrapped cobalt materials calcined at 750 degreesC efficiently catalyzed the epoxidation of (Z)-cyclooctene using iodozylbenzene as the oxygen donor. (C) 2003 Elsevier B.V. All rights reserved.

Titanium(IV)-EDTA complex - Kinetics of thermal decomposition by non-isothermal procedures

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=172.4 +/- 9.7 and 205.3 +/- 12.8 kJ mol(-1), and pre-exponential factor: logA = 16.38 +/- 0.84 and 18.96 +/- 1.21 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 Malek 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.

Thermal studies on nickel(II) 4-iodopyrazole complexes

This work describes the synthesis, IR and UV-Vis spectroscopic characterization as well the thermal behavior of the [NiCl2(HIPz)(4)]center dot C3H6O (1), [Ni(H2O)(2)(HIPz)(4)](NO3)(2) (2), [Ni(NCS)(2)(HIPz)(4)] (3) and [Ni(N-3)(2)(HIPz)(4)] (4) (HIPz = 4-iodopyrazole) pyrazolyl complexes. TG experiments reveal that the compounds 1-4 undergo thermal decomposition in three or four mass loss steps yielding NiO as final residue, which was identified by X-ray powder diffraction.

Thermal behaviour of polymetallic metal carbonyls with Fe-Fe, Fe-Hg and Hg-Hg bonds containing Lewis bases.

The thermal behaviour of polymetallic metal carbonyls containing Fe-Fe, Fe-Hg and Hg-Hg bonds and Lewis bases, such as [Fe-3(CO)(8)(L)(2)] (L = 1,10-phenantroline,2,2'-bipyridine), [Fe(CO)(4)(HgCl)(2)] and [Fe(CO)(4)(HgCl)(2)(L)(2)] (L = 1,10-phenantroline,2-quinolinethiol), have been investigated by thermal analysis (TG), Thermal studies give evidence that the thermal decomposition mechanisms and starting temperatures are strongly influenced by the Lewis bases. The thermal decompositions under synthetic air yielded, in all cases, the final solid product Fe2O3 which presence was confirmed by X-ray powder diffraction technique.

Influence of the thermal treatment in the crystallization of NiWO4 and ZnWO4

NiWO4 and ZnWO4 were synthesized by the polymeric precursor method at low temperatures with zinc or nickel carbonate as secondary phase. The materials were characterized by thermal analysis (TG/DTA), infrared spectroscopy, UV-Vis spectroscopy and X-ray diffraction. NiWO4 was crystalline after calcination at 350 A degrees C/12 h while ZnWO4 only crystallized after calcination at 400 A degrees C for 2 h. Thermal decomposition of the powder precursor of NiWO4 heat treated for 12 h had one exothermic transition, while the precursor heat treated for 24 h had one more step between 600 and 800 A degrees C with a small mass gain. Powder precursor of ZnWO4 presented three exothermic transitions, with peak temperatures and mass losses higher than NiWO4 has indicating that nickel made carbon elimination easier.

Thermogravimetry on calcined mass basis - hydrated cement phases and pozzolanic activity quantitative analysis

When cement hydrated compositions are analyzed by usual initial mass basis TG curves to calculate mass losses, the higher is the amount of additive added or is the combined water content, the higher is the cement 'dilution' in the initial mass of the sample. In such cases, smaller mass changes in the different mass loss steps are obtained, due to the actual smaller content of cement in the initial mass compositions. To have a same mass basis of comparison, and to avoid erroneous results of initial components content there from, thermal analysis data and curves have to be transformed on cement calcined basis, i.e. on the basis of cement oxides mass present in the calcined samples or on the sample cement initial mass basis.The paper shows and discusses the fundamentals of these bases of calculation, with examples on free and combined water analysis, on calcium sulfate hydration during false cement set and on quantitative evaluation and comparison of pozzolanic materials activity.

Completeness of beta-phase decomposition reaction in Cu-Al-Ag alloys

The completeness of beta-phase decomposition reaction in the Cu-11wt%Al-xwt%Ag alloys (x = 0, 1, 2, and 3) was studied using differential scanning calorimetry (DSC), X-ray diffractometry (XRD), and optical microscopy (OM). The results indicated that beta-phase transformations are highly dependent on cooling rate and on the presence of Ag. on slow cooling, the silver presence prevents the beta- and beta(1)-phase decomposition; thus, inducing the martensitic phase formation. After rapid cooling, a new thermal event is observed and the reverse martensitic transformation is shifted to lower temperatures.

Thermal behaviour of corn starch granules under action of fungal alpha-amylase

Corn starch, partially hydrolyzed by fungal alpha-amylase was investigated by using thermal analysis, microscopy and X-ray diffraction. After enzymatic treatment lower degradation onset temperatures were observed. DSC analysis showed almost similar range of gelatinization temperature, however, the enthalpies of gelatinization increased for the partially hydrolyzed starch granules. According to the X-ray diffraction analysis, stronger cereal pattern peaks were recognized after enzymatic digestion. The results suggested that the hydrolysis was more pronounced in the amorphous part of the starch granules.

Thermal study of mononuclear Pd(II) complexes of the type [Pd(X)(2)(Rtu)(PPh3)] (X = Cl, SCN; Rtu = N-methylthiourea, N-phenylthiourea)

The synthesis, spectroscopic characterization, and thermal analysis of the compounds [Pd(X)(2)(mtu)(PPh3)] (X = Cl- (1), SCN- (2); mtu = N-methylthiourea; PPh3 = triphenylphosphine) and [Pd(X)(2)(phtu)(PPh3)] (X = Cl- (3), SCN- (4); phtu = N-phenylthiourea) are described. The thermal decomposition of the compounds occurs in two, three, or four stages and the final decomposition products were identified as Pd-0 by X-ray powder diffraction. The thermal stability order of the complexes is 4 > 3 > 2 > 1.

Preparation and thermal characterization of inclusion complex of Brazilian green propolis and hydroxypropyl-beta-cyclodextrin

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Thermal and structural characterization of SrTi(1-x)Nd(x)O(3)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Chemical and spectroscopic studies of a new palladium(II) complex with N-acetyl-L-cysteine

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)