Avaliação termoanalítica da eficiência de antioxidantes na estabilidade oxidativa do biodiesel de mamona

The biodiesel is defined as the mono-alkyl ester derived from long-chain fatty acids, from renewable sources such as vegetable oils or animal fat, whose use is associated with the replacement of fossil fuels in diesel engine cycle. The biodiesel is susceptible to oxidation when exposed to air and this process of oxidation affects the quality of fuel, mainly due to long periods of storage. Because of this, the oxidation stability has been the focus of numerous researches since it directly affects the producers, distributors and users of fuel. One of the possibilities to increase the resistance of biodiesel is the autoxidation treatment with inhibitors of oxidation. The antioxidants can be used as potential inhibitors of the effects of oxidation on the kinematic viscosity and the index of acidity of biodiesel, thereby increasing oxidative stability. This work aims to examine the efficiency of antioxidants, α-tocopherol and butylated hydroxy-toluene (BHT), added the biodiesel content of remembrance through Pressurized-Differential Scanning Calorimetry (P-DSC), Thermogravimetry (TG) and Petrology. The results showed that the use of antioxidant BHT, at the concentration of 2000ppm, increased resistance to oxidation of the biodiesel and oxidative induction time (OIT), which is a better result as antioxidant than the α-tocopherol. With the thermogravimetric analysis, it was observed that the biodiesel presented an initial decomposition temperature of lower tendency than that of oil, demonstrating to be more volatile, bearing great similarity to the diesel and being characterized as an alternative fuel. The rheological analysis indicated that each sample of biodiesel behaved as a Newtonian fluid

Avaliação da estabilidade térmica e oxidativa do biodiesel de algodão e do efeito da adição de antioxidantes (α-tocoferol e BHT)

This work aims to study the effects of adding antioxidants, such as, α- tocopherol and BHT on the thermal and oxidative stability of biodiesel from cottonseed (B100). The Biodiesel was obtained through the methylical and ethylical routes. The main physical and chemical properties of cotton seed oil and the B100 were determined and characterized by FTIR and GC. The study of the efficiency of antioxidants, mentioned above, in concentrations of 200, 500, 1000, 1500, 2000ppm, to thermal and oxidative stability, was achieved by Thermogravimetry (TG), Differential Thermal Analysis (DTA), Differential Scanning Calorimetry (DSC), Differential Scanning Calorimetry - Hi-Pressure (P-DSC) and Rancimat. The Biodiesel obtained are within the specifications laid down by Resolution of ANP No7/2008. The results of TG curves show that the addition of both antioxidants, even in the lowest concentration, increases the thermal stability of Biodieseis. Through the DTA and DSC it was possible to study the physical and chemical transitions occurred in the process of volatilization and decomposition of the material under study. The initial time (OT) and temperature (Tp) of oxidation were determined through the P-DSC curve and they showed that the α-tocopherol has a pro-oxidant behavior for some high concentrations. The BHT showed better results than the α-tocopherol, with regard to the resistance to oxidation

Estudo da influência do biodiesel de mamona como aditivo antioxidante para o biodiesel de girassol e soja

Biodiesel is a fuel made up by mono-alkyl-esters of long chain fatty acids, derived from vegetable oils or animal fat. This fuel can be used in compression ignition engines for automotive propulsion or energy generation, as a partial or total substitute of fossil diesel fuel. Biodiesel can be processed from different mechanisms. Transesterification is the most common process for obtaining biodiesel, in which an ester compound reacts with an alcohol to form a new ester and a new alcohol. These reactions are normally catalyzed by the addition of an acid or a base. Initially sunflower, castor and soybean oil physicochemical properties are determined according to standard test methods, to evaluate if they had favorable conditions for use as raw material in the transesterification reaction. Sunflower, castor and soybean biodiesel were obtained by the methylic transesterification route in the presence of KOH and presented a yield above 93% m/m. The sunflower/castor and soybean/castor blends were studied with the aim of evaluating the thermal and oxidative stability of the biofuels. The biodiesel and blends were characterized by acid value, iodine value, density, flash point, sulfur content, and content of methanol and esters by gas chromatography (GC). Also studies of thermal and oxidative stability by Thermogravimetry (TG), Differential Scanning Calorimetry High Pressure (P-DSC) and dynamic method exothermic and Rancimat were carried out. Biodiesel sunflower and soybean are presented according to the specifications established by the Resolution ANP no 7/2008. Biodiesel from castor oil, as expected, showed a high density and kinematic viscosity. For the blends studied, the concentration of castor biodiesel to increased the density, kinematic viscosity and flash point. The addition of castor biodiesel as antioxidant in sunflower and soybean biodiesels is promising, for a significant improvement in resistance to autoxidation and therefore on its oxidative stability. The blends showed that compliance with the requirements of the ANP have been included in the range of 20-40%. This form may be used as a partial substitute of fossil diesel

Avaliação por SAXS e DSC das interações entre H2O e Renex-100

The aggregation behavior of the non-ionic surfactant Renex-100 in aqueous solutions and mesophases was evaluated by SAXS in a wide range of concentrations, between 20 and 30 °C. Complementary, water interactions were defined by DSC curves around 0°C. SAXS showed that the system undergoes the following phase transitions, from diluted to concentrated aqueous solutions: 1) isotropic solution of Renex aggregates; 2) hexagonal mesophase; 3) lamellar mesophase; and 4) isotropic solution. DSC analysis indicated the presence of interfacial water above 70wt%, which agreed with the segregation of free water to form the structural mesophases observed by SAXS bellow this concentration.

The influence of crucible material on the DSC thermal analysis compared to freeze-drying microscopy results

The aim of this study was to investigate the influence of different crucible materials on the thermal analysis of binary systems. The thermal properties of two distinct solutions were measured both by Differential Scanning Calorimetry (DSC) and freeze-drying microscopy and the results were compared. The glass transition of the maximally freeze-concentrate (T (g)`) and the eutectic melting temperature (T (eut)) were not influenced by the crucible material. However the heat of fusion (Delta H) involved during the T (eut) as well as the Delta C (p) involved during the T (g)` of the solutions were affected.

DSC estimation of structural and textural parameters of SBA-15 silica using water probe

The aim of this study was to use DSC and X-ray diffraction measurements to determine the pore size and pore wall thickness of highly ordered SBA-15 materials. The DSC curves showed two endothermic events during the heating cycle. These events were due to the presence of water inside and outside of mesopores. The results of pore radius, wall thickness and pore volume measurements were in good agreement with the results obtained by nitrogen adsorption measurement, XRD and transmission electron microscopy.

Analysis of thermal properties of phase change materials (PCM) using differential scanning calorimeter (DSC)

Commercially available PCM RT 20, RT 27, SP 22, A17 and SP 25 A8. Were analyzed using dynamic and step method of heat flux DSC. The results of the dinamic and step method were compared with commercial valures. It was found that RT 20 & RT 27 showed good conforming of results with commercial values while SP 22 A17 & SP 25 A8 did not show conformity.

Factors influencing the dissolution of phosphate rock in a range of high P-fixing soils from Cameroon

A laboratory incubation experiment was conducted to evaluate the soil factors that influence the dissolution of two phosphate rocks (PRs) of different reactivity (Gafsa, GPR, reactive PR; and Togo-Hahotoe, HPR, low reactivity PR) in seven agricultural soils from Cameroon having variable phosphorus (P)- sorption capacities, organic carbon (C) contents, and exchangeable acidities. Ground PR was mixed with the soils at a rate of 500 mg P kg 21 soil and incubated at 30 degrees C for 85 days. Dissolution of the PRs was determined at various intervals using the Delta NaOH-P method ( the difference of the amount of P extracted by 0.5 M NaOH between the PR-treated soils and the control). Between 4 and 27% of HPR and 33 and 50% of GPR were dissolved in the soils. Calcium (Ca) saturation of cation exchange sites and proton supply strongly affected PR dissolution in these soils. Acid soils with pH-(H2O), < 5 (NKL, ODJ, NSM, MTF) dissolved more phosphate rock than those with pH-(H2O) > 5 (DSC, FGT, BAF). However, the lack of a sufficient Ca sink in the former constrained the dissolution of both PRs. The dissolution of GPR in the slightly acidic soils was limited by increase in Ca saturation and that of HPR was constrained by limited supply in protons. Generally, the dissolution of GPR was higher than that of HPR for each soil. The kinetics of dissolution of PR in the soils was best described by the power function equation P At B. More efficient use of PR in these soils can be achieved by raising the soil cation exchange capacity, thereby increasing the Ca sink size. This could be done by amending such soils with organic materials.

Development of novel methods to determine crystalline glucose content of honey based on DSC, HPLC, and viscosity measurements and their use to examine the setting propensity of honey

Crystallization must occur in honey in order to produce set or creamed honey; however, the process must occur in a controlled manner in order to obtain an acceptable product. As a consequence, reliable methods are needed to measure the crystal content of honey (φ expressed as kg crystal per kg honey), which can also be implemented with relative ease in industrial production facilities. Unfortunately, suitable methods do not currently exist. This article reports on the development of 2 independent offline methods to measure the crystal content in honey based on differential scanning calorimetry and high-performance liquid chromatography. The 2 methods gave highly consistent results on the basis of paired t-test involving 143 experimental points (P > 0.05, r**2 = 0.99). The crystal content also correlated with the relative viscosity, defined as the ratio of the viscosity of crystal containing honey to that of the same honey when all crystals are dissolved, giving the following correlation: μr = 1 + 1398.8∅**2.318. This correlation can be used to estimate the crystal content of honey in industrial production facilities. The crystal growth rate at a temperature of 14 ◦C—the normal crystallization temperature used in practice—was linear, and the growth rate also increased with the total glucose content in the honey.

Thermal characterization of dental composites by TG/DTG and DSC

Dental composites can be improved by heat treatment, as a possible way to increase mechanical properties due to additional cure (post-cure). Direct dental composites are essentially similar to the indirect ones, supposing they have the same indication. Therefore, to establish a heat treatment protocol for direct composites, using as indirect (photoactivated by continuous and pulse-delay techniques), a characterization (TG/DTG and DSC) is necessary to determine parameters, such as mass loss by thermal decomposition, heat of reaction and glass transition temperature (T (g)). By the results of this study, a heat treatment could be carried out above 160 A degrees C (above T (g), and even higher than the endset exothermic event) and under 180 A degrees C (temperature of significant initial mass loss).

Resinas poliésteres carboxifuncionais para tinta em pó : caracterização e estudo cinético da reação de cura

Um grande desafio relacionado à química da resina poliéster carboxifuncional, para aplicação em tinta em pó, é conseguir um balanço adequado entre a sua massa molar, funcionalidade, viscosidade e temperatura de transição vítrea (Tg). Essas características devem permitir a aplicação da resina na produção de tinta em pó na qual seja possível a obtenção de boa estabilidade durante sua estocagem e ótimas propriedades mecânicas durante a sua vida útil. Nesta tese, desenvolveu-se a introdução de uma metodologia para a caracterização de resinas poliésteres carboxifuncionais para aplicação em tinta em pó, baseada em reometria capilar e calorimetria diferencial de varredura (DSC). Esta se diferencia daquela baseada em métodos usuais muito subjetivos, usados corriqueiramente no controle do processo de síntese destas resinas. Os resultados de DSC mostram que todas as resinas poliésteres carboxifuncionais sintetizadas neste trabalho são completamente amorfas, sendo a Tg um parâmetro sensível à modificação da composição da resina. A determinação da viscosidade de cisalhamento das resinas utilizando reômetro capilar em comparação a outras técnicas usuais, permite a obtenção de valores mais absolutos, independente da ordem de grandeza da massa molar e da funcionalidade da resina, demonstrando ser uma técnica simples, eficaz e de grande utilidade em relação às atualmente utilizadas. A utilização da técnica de DSC permitiu avaliar a cinética da reação de cura do sistema poliéster/triglicidilisocianurato (TGIC) através de métodos cinéticos isotérmicos e dinâmicos. Através do método isotérmico determinou-se o grau de conversão da reação para vários tempos de cura, e pelos métodos dinâmicos de Kissinger, Osawa e Meia Largura determinou-se a energia de ativação da cura.

Thermomechanical characterization of PVDF and P(VDF-TrFE) blends containing corn starch and natural rubber

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

DSC studies on protein isolate of guava seeds Psidium guajava

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Crystallization kinetics in phosphate sodium-based glass studied by DSC technique

In this work, differential scanning calorimetry (DSC) was used to study the mechanism of crystallization of 5OP(2)O(5-)27.8Na(2)O-16ZnO-6.2Al(2)O(3) glass. DSC measurements were performed on bulk and powdered glasses with different particle size. The curve for bulk glass shows one crystallization peak while powdered glasses presented two distinct crystallization peaks. Based on DSC studies, the activation energies obtained were 336 +/- 6 and 213 +/- 3 U mol(-1), associated with first and second crystallization peaks, respectively. Analyzing the DSC parameters as a function of particle size, the Avrami n parameter suggests that the peak at low temperature may be associated with surface crystallization while the peak at high temperature is associated with bulk crystallization. (C) 2002 Elsevier B.V. Ltd. All rights reserved.

DSC studies on crystallization mechanisms of tellurite glasses

The purpose of this work is to study the 20Li(2)O-80TeO(2) glass using the differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques in order to understand the crystallization kinetics on this glass matrix. To study the glass by DSC, screened samples with different particle sizes to resolve the observed asymmetrical crystallization peak were used. DSC curves for particles smaller than 38 mum in size show two distinct crystallization peaks, associated to distinct phase transformation in this glass, leading to activation energies at 301 and 488 kJ mol(-1). XRD analysis reveals that the first crystallization peak is attributed to TeO2 crystalline phase while the second one to the alpha-TeO3 and an unidentified phase.(C) 2004 Elsevier B.V. All rights reserved.