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Abstract  

Commercial light-cured dental composites were used in this study. Two laboratorial composites, Resilab (Wilcos/Brazil), Epricord (Kuraray/Japan) were compared under cured and uncured conditions. Thermal analysis, infrared spectroscopy and scanning electron microscopy were used to evaluate the dental composites. The mass change and heat flow signals (TG–DSC) were recorded simultaneously by using STA 409 PC Luxx (NETZSCH), in the 25–800 °C temperature range at a heating rate of 10 °C/min under nitrogen atmosphere (70 mL/min). Employing thermo-microbalance TG 209 C F1 Iris (NETZSCH) coupled to the BRUKER Optics FTIR TENSOR, the samples were analyzed by combined thermogravimetric and spectroscopic methods (TG–FTIR). The initial sample mass was about ~12 mg, the data collection have been done in the 35–800 °C temperature range at a heating rate of 20 K/min in nitrogen atmosphere (flow rate: 40 mL/min). Finally, superficial topographic was analyzed by scanning electron microscopy (SEM). Dental composite evaluation suggests a high thermal stability and inorganic content in RES D sample. Degrees of conversion (DC) values were almost the same and there was no direct relationship between DC and amount of particles and size. Similar compositions were found in all samples.

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Abstract  

The properties of polymeric blends originate from the synergistic association of their components. In this investigation, phenolic resins obtained by the reaction of cashew-nut shell liquid (CNSL) and aldehyde are used in several applications. Mixtures of CNSL with industrial reject ethylene-co-vinyl acetate (EVA reject) were prepared with an EVA reject content up to 70%. The thermal compatibility and stability were evaluated by means of thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). For blends containing a high percentage of EVA reject, the TG curves clearly show two decomposition stages, one at 350‡C and the other at 450‡C (onset 467‡C). The DIG curves of the blend containing 70% CNSL exhibit decomposition at 240‡C. The DSC curves show that the samples containing a high percentage of EVA reject are incompatible, withT g values around −30‡C.

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Abstract  

Thermal degradation of granite and marble industry reject (GMIR), a red clay (RC)and their composites were studied by non-isothermal thermogravimetry (TG/DTG) in nitrogen atmosphere, differential thermal analysis (DTA) and derivative thermogravimetry(DTG) in air atmosphere. Measurements were made in the temperature range of 25–1000,25–1200 and 25–1400C. The kinetic parameters were determined by Flynn–Wall and Kissinger's methods. The results indicate the absent dominance of one mechanism of reaction, and the composites show smaller values of kinetic parameters than GMIR or RC.

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Abstract  

The thermogravimetric analysis (TG) of two series of tri-block copolymers based on poly(L,L-lactide) (PLLA) and poly(ethyleneglycol) (PEG) segments, having molar mass of 4000 or 600 g mol–1, respectively, is reported. The prepared block copolymers presented wide range of molecular masses (800 to 47500 g mol–1) and compositions (16 to 80 mass% PEG). The thermal stability increased with the PLLA and/or PEG segment size and the tri-block copolymers prepared from PEG 4000 started to decompose at higher temperatures compared to those copolymers from PEG 600. The copolymers compositions were determined by thermogravimetric analysis and the results were compared to other traditional quantitative spectroscopic methods, hydrogen nuclear magnetic resonance spectrometry (1HNMR) and Fourier transform infrared spectrometry (FTIR). The PEG 4000 copolymer compositions calculated by TG and by 1HNMR, presented differences of 1%, demonstrating feasibility of using thermogravimetric analysis for quantitative purposes.

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Abstract  

The aim of this study is to understand some properties and thermal behavior of blood, giving a possible alternative tool which differs from the traditional blood diagnostic methods, and to improve investigations in hematology and artificial bloods. Wistar rat blood samples (WRBS); SHR rat blood samples (SHRBS) and human blood samples (HBS) were analyzed. TG curves showed two decomposition stages for HBS at around 100 and 230C (T onset), while three mass degradation stages for WRBS (70, 110, 270C) and SHRBS (70, 120, 270C) could be observed. DSC peaks showed five endotherms for HBS at 65, 82, 194, 201 and 309C and three endotherms for WRBS at 83, 184 and 313C.

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Abstract  

Polyurethane composites with bagasse of sugar cane (BSC) at different proportions: 5, 10 and 20 mass/mass% were prepared by melt mixing method. The thermal behavior of these composites were studied by thermogravimetry (TG/DTG). The influence of fiber concentration on the kinetic parameters of the composites was studied and a better interaction was suggested between PU/BSC with 5mass/mass% of fiber. Scanning electron microscopy was carried out to investigate surface morphology.

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Abstract  

The thermal behavior of the kidney, heart and liver of spontaneous hypertension rats (SHR) were studied by thermogravimetry (TG) and differential thermal analysis (DTA). SHR are, by far, the most widely used rat model in the study of heart diseases in mammals, because they develop chronic hypertension, which leads to heart failure during their lives. TG curves showed two steps for all samples: at 800C less residues remained for an SHR kidney (4.01.8%) than for an SHR heart (6.90.4) and liver samples (7.51.9%). It probably happened due to the presence of inorganic substances such as iron, calcium, magnesium, potassium and sodium. DTA curves depicted three endothermic events for kidney (70, 120 and 310C), heart (85, 250 and 300C) and liver samples (70, 250 and 310C), indicating protein denaturation, as well as protein degradation and fat degradation, respectively. TG/DTG/DTA profiles of organs samples showed peculiarities that permit correlation between them. These methods might serve as a simple alternative to investigations over these vital organs.

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Abstract  

Samples of poly(l,l-lactide)-block-poly(ethylene glycol)-block-poly(l,l-lactide) (PLLA-PEG-PLLA) were synthesized from l,l-lactide polymerization using stannous 2-ethylhexanoate, Sn(Oct)2 as initiator and di-hydroxy-terminated poly(ethylene glycol) (PEG) (M n = 4000 g mol−1) as co-initiator. The chemical linkage between the PEG segment and the PLA segments was characterized by Fourier transform infrared spectroscopy (FTIR). Thermogravimetry analysis (TG) revealed the copolymers composition and was capable to show the deleterious effect of an excess of Sn(Oct)2 in the polymer thermal stability, while Differential Scanning Calorimetry (DSC) allowed the observation of the miscibility between the PLLA and PEG segments in the different copolymers.

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Abstract  

Enhanced oil recovery process is based on the injection of chemical products (e.g. polymers, surfactants, gases) or thermal energy (originating from the injection of e.g. steam, hot water, in situ combustion) to recover crude oil. One of these processes use polymer solution to mobilize the oil in the reservoir. In this work the thermal decomposition kinetic of xanthan gum, guar gum and a blend (50/50 mass/mass%) was studied according to Ozawa–Flynn–Wall method. According to the kinetic analysis, the studied systems were copmpatible. The rheological behavior of the samples was studied in distilled water and seawater at different temperatures. Only the blend was studied in distilled water presented synergism (enhancement in material properties like stability and viscosity) which was confirmed through rheology.

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Journal of Thermal Analysis and Calorimetry
Authors: C. G. Mothé, T. Carestiato, M. B. Aguila, and C. A. Mandarim-de-Lacerda

Summary Hypertension is a major and growing public health problem. It is responsible for the mortality of millions of people around world, and is increasing each year. Nevertheless, the understanding of the relationship between the composition of the heart's cells, hypertension and health diseases is still very incomplete. The present study focuses on the evaluation of the attributes of some hearts of Spontaneous Hypertension Rats (SHR), comparing with SHR which received additional amounts of polysaccharide (SHR+P) and with wistar rats (normal blood pressure) by Thermal Analysis. Some differences could be seen between groups, as the residue content after 800°C was different for rats from different groups, and of wistar rats hearts samples showed 5.3±0.3& of residues vs. 8.3±1.5& of the SHR. DSC profiles for wistar rats showed one intense endothermic event at 160°C, with enthalpy transition of 450 J g-1 and more three small events. Thermal analyses curves also showed some differences between freezing and no freezing samples, probably associated to the denaturation of proteins and degradation of organic materials.

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