Thermal and photochemical stability of poly(vinyl alcohol)/modified lignin blends

A kraft lignin derivative (KLD) obtained by reaction with p-aminobenzoic acid/phthalic anhydride was blended with poly(vinyl alcohol) (PVA) by solution casting from DMSO. PVA and PVA/KLD films were exposed to ultraviolet radiation (24, 48, and 96 h) and analyzed by thermogravimetry (TG), differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance (H-1 NMR) spectroscopy, and scanning electron microscopy (SEM). PVA films show a loss of thermal stability due to irradiation. PVA/KLD reveals greater thermal stability than PVA and an increase in thermal stability after irradiation. These results suggest that the incorporation of KLD into PVA provides a gain in thermal and photochemical stability. FTIR, H-1 NMR, DSC, and TG results obtained for the blends suggest that intermolecular interactions between PVA and KLD chains are present. SEM micrographs revealed blend miscibility for a KLD blend content of up to 15 wt%, as observed at magnification of 1000 times. (c) 2005 Elsevier Ltd. All rights reserved.

On the temperature stability of extracellular hemoglobin of Glossoscolex paulistus, at different oxidation states: SAXS and DLS studies

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

Thermal Decomposition Kinetics of Humic Substances Extracted from Mid-Rio Negro (Amazon Basin) Soil Samples

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Thermal analysis of chitosan based networks

In this work two kinds of material were studied: chitosan cross-linked with glutaraldehyde and in a blend with PEO. The resulting products as well as chitosan and PEO raw materials, were analyzed by TG/DTG, DSC and DMTA to determinate the in?uence of cross-linking and PEO addition on thermal properties of the resulting materials. It was observed by thermogravimetry that the water-polymer interaction will be different for the cross-linked material compared to the blend, according to the specific site availability. The in?uence of such modifications (cross-linking and PEO addition), on chitosan thermal stability was also studied. The DSC results showed a good agreement with the TG/DTG results, reinforcing the interpretation given for TG/DTG results. DMTA results indicate that glass transition temperature is around 50 degrees C for the polymer under study. (c) 2005 Elsevier Ltd. All rights reserved.

Evaluation of thermal behavior of latex membranes from genetically improved rubber tree (Hevea brasiliensis)

Thermal stability, thermal decomposition process, residual mass, temperature of glass transition (T-g) and temperature dependence of storage modulus (E'), were determined for latex membranes prepared from six clones of Hevea brasiliensis: IAC 331, IAC 332, IAC 333 and IAC 334 grown at experimental plantations of Instituto Agronomico de Campinas (IAC) in Votuporanga, São Paulo State, Brazil. Latex membranes from GT1 and RRIM 600 Asian matrix clones were used as references. The thermal behavior of latex membranes from genetically improved rubber trees was characterized using thermogravimetry/derivative thermogravimetry (TG/DTG), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The thermal behavior of latex from clones studied in the present work showed similar features of the clones previously reported (IAC 40, IAC 300, IAC 301, IAC 328, IAC 329 and IAC 330), with mass loss in four consecutive steps, except IAC 333, which showed an additional mass loss step. (c) 2006 Elsevier B.V. All rights reserved.

New palladium(II) complexes with pyrazole ligands Part II. Synthesis, spectral and thermal studies, and antitumor evaluation

This study describes the synthesis, IR, (1)H, and (13)C{(1)H} NMR spectroscopic as well the thermal characterization of the new palladium(II) pyrazolyl complexes [PdCl(2)(HmPz)(2)] 1, [PdBr(2)(HmPz)(2)] 2, [PdI(2)(HmPz)(2)] 3, [Pd(SCN)(2)(HmPz)(2)] 4 {HmPz = 4-methylpyrazole}. The residues of the thermal decomposition were identified as Pd(0) by X-ray powder diffraction. From the initial decomposition temperatures, the thermal stability of the complexes can be ordered in the sequence: 1 > 2 > 4 a parts per thousand 3. The cytotoxic activities of the complexes and the ligand were investigated against two murine cancer cell lines: mammary adenocarcinoma (LM3) and lung adenocarcinoma (LP07) and compared to cisplatin under the same experimental conditions.

Mono- and dinuclear palladium(II) compounds containing N,S donor ligands - Synthesis, characterization and thermal behavior

Synthesis, spectroscopic characterization and thermal analysis of the compounds [Pd-2(dmba)(2)(mu-NCO)(mu-2-qnS)] (1), [Pd-2(dmba)(2)(mu-NCO)(mu-8-qnS)] (2), [Pd(2-qnS)(2)] (3) and [Pd(8-qn(S))2] (4) (dmba=N,N-dimethylbenzylamine; 2-qnS=2-quinolinethiolate; 8-qnS=8-quinolinethiolate) are described. The thermal decomposition of these compounds occurs in four consecutive steps 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 > 1 > 2.

Thermal study and physico-chemical characterization of some functional properties of guava seeds protein isolate (Psidium guajava)

The guava seed protein isolate ( PI) was obtained from the protein precipitation belonging to the class of the gluteline (Ip 4.5). The conditions for the preparation of the PI were determined by both the solubility curve and simultaneous thermogravimetry-differential thermal analysis (TG-DTA): pH 11.5, absence of NaCl and whiteners and T=( 25 +/- 3) degrees C. Under these conditions a yield of 77.0 +/- 0.4%, protein content of 94.2 +/- 0.3, ashes 0.50 +/- 0.05% and thermal stability, T= 200 degrees C, were obtained. The TG-DTA curves and the PI emulsification capacity study showed the presence of hydrophobic microdomains at pH 11.5 and 3.0 suggesting a random coil protein conformation and, to pH 10.0, an open protein conformation. The capacity of emulsification (CE), in the absence of NaCl, was verified for: 1 - pH 3.0 and 8.5, using the IP extracted at pH 10.0 and 11.5, CE >= 343 +/- 5 g of emulsified oil/g of protein; 2 - pH 6.60 just for the PI obtained at pH 11.5, CE >= 140 +/- 8 g of emulsified oil/g of protein.

Thermal characterization of solid lipid nanoparticles containing praziquantel

Solid lipid nanoparticles (SLNs), loaded and unloaded with praziquantel (PRZ-load SLN and PRZ-unload SLN) were prepared by two different procedures: (a) oil-in-water hot microemulsion method, obtaining at 70 degrees C an optically transparent blend composed of surfactant, co-surfactant, and water; and (b) oil-in-water microemulsion method, dissolving the lipid in an immiscible organic solvent, emulsified in water containing surfactants and co-surfactant, and then evaporated under reduced pressure at 50 degrees C. The mean diameter, polydispersity index (PdI), and zeta potential were 187 to 665 nm, 0.300 to 0.655, and -25 to -28 mV respectively, depending on the preparation method. The components, binary mixture, SLNs loaded and unloaded with PRZ, and physical mixture were evaluated by differential scanning calorimetry (DSC) and thermogravimetry (TG). The non-isothermal isoconversional Flynn-Wall-Ozawa method was used to determine the kinetic parameters associated with the thermal decomposition of the samples. The experimental data indicated a linear relationship between the apparent activation energy E and the pre-exponential factor A, also called the kinetic compensation effect (KCE), allowing us to determine the stability with respect to the preparation method. Loading with PRZ increased the thermal stability of the SLNs.

Synthesis, characterization and thermal studies on solid 3-methoxybenzoate of some bivalent transition metal ions

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

Synthesis, characterization and thermal studies of solid state 4-methylbenzylidenepyruvate of some trivalent metal ions

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

Synthesis, characterization and thermal behaviour of solid-state compounds of benzoates with some bivalent transition metal ions

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

Synthesis and thermal studies of solid state 2-chloro-benzylidenepyruvic acid and its compounds with sodium, aluminium (III), gallium (III) and indium (III) cations

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

Thermal analysis as a screening technique for the characterization of babassu flour and its solid fractions after acid and enzymatic hydrolysis

The babassu (Orbignya phalerata) is a native tree found in northern Brazil. Extracts of the babassu coconut have been widely used in industry. Babassu flour has about 60% starch, thus, besides nourishment it can be used as an alternative biofuel source. However, the properties of this starch lack of study and understanding. The main purpose of this study was to investigate the thermal behavior of raw babassu flour and its solid hydrolyzed fraction. The analyses were carried out using SHIMADZU DSC and TG thermic analyzers. The results demonstrated a reduction in thermal stability of the solid hydrolyzed fraction compared to raw matter. The kinetic parameters were investigated using non-isothermal methods and the parameters obtained for its decomposition process were an E(a) of 166.86 kJ mol(-1) and a frequency factor (beta) of 6.283 x 1014 min(-1); this was determined to be a first order reaction (n = 1). (C) 2011 Elsevier B.V. All rights reserved.

Cellulose nanowhiskers from coconut husk fibers: Effect of preparation conditions on their thermal and morphological behavior

Cellulose nanowhiskers were prepared by sulfuric acid hydrolysis from coconut husk fibers which had previously been submitted to a delignification process. The effects of preparation conditions on the thermal and morphological behavior of the nanocrystals were investigated. Cellulose nanowhisker suspensions were characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and X-ray diffraction. Results showed that it was possible to obtain ultrathin cellulose nanowhiskers with diameters as low as 5 nm and aspect ratio of up to 60. A possible correlation between preparation conditions and particle size was not observed. Higher residual lignin content was found to increase thermal stability indicating that by controlling reaction conditions one can tailor the thermal properties of the nanowhiskers. Published by Elsevier Ltd.