Navegando por Palavras-chave "Thermal analysis"
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- ItemSomente MetadadadosAg-rich precipitates formation in the Cu-11%Al-10%Mn-3%Ag alloy(Elsevier B.V., 2014-12-05) Silva, R. A. G. [UNIFESP]; Paganotti, A. [UNIFESP]; Jabase, L. [UNIFESP]; Adorno, A. T.; Carvalho, T. M.; Santos, C. M. A.; Universidade Federal de São Paulo (UNIFESP); UNESPThe formation of Ag-rich precipitates in the Cu-11%Al-10%Mn-3%Ag alloy initially quenched from 1123 K was analyzed. the results showed that nanoprecipitates of a Cu-rich phase are produced at about 523 K. in higher temperatures these nanoparticles grow and the relative fraction of Ag dissolved in it is increased, thus forming the Ag-rich phase. (C) 2013 Elsevier B.V. All rights reserved.
- ItemSomente MetadadadosCharacterization and evaluation of free and nanostructured ursolic acid incorporated in cosmetic formulation using thermal analysis(Springer, 2014-03-01) Almeida, Mariana Mandelli de; Bou-Chacra, Nadia Araci; Ribeiro de Castro Lima, Cibele Rosana; Matos, Jivaldo do Rosario; Moscardini Filho, Elder [UNIFESP]; Mercuri, Lucildes Pita [UNIFESP]; Baby, Andre Rolim; Kaneko, Telma Mary; Robles Velasco, Maria Valeria; Universidade de São Paulo (USP); Universidade Federal de São Paulo (UNIFESP)The ursolic acid (UA) increases the skin's barrier function and acts in epidermal differentiation of keratinocytes in the epidermis, promoting cell renewal. Besides the mentioned properties UA also has antioxidant, antimicrobial, and anti-irritant functions to cosmetic formulations. Thus, it is necessary formulation studies to insure the development of quality cosmetic products containing this active, increasing its antioxidant potential within nanoparticles. This study aims to characterize and evaluate the thermal behavior of UA in free and nanostructured forms, and both incorporated into a cosmetic base formulation, using thermogravimetry and differential scanning calorimetry. Through the study were observed that free UA, in the embedded nanoparticles and in base formulation exhibited different behavior in similar thermal profile and relative to the presence of UA. the UA remained stable to a temperature of 250 A degrees C and the technique has been shown to be effective for characterizing UA, evaluate water content, and stability of the formulation base.
- ItemSomente MetadadadosComparative physical-chemical characterization of encapsulated lipid-based isotretinoin products assessed by particle size distribution and thermal behavior analyses(Elsevier B.V., 2010-06-10) Guimaraes, Carla Aiolfi; Menaa, Farid; Menaa, Bouzid; Quenca-Guillen, Joyce S.; Matos, Jivaldo do Rosario; Mercuri, Lucildes Pita [UNIFESP]; Braz, Andre Borges; Rossetti, Fabia Cristina; Maria Kedor-Hackmann, Erika Rosa; Rocha Miritello Santoro, Maria Ines; Universidade de São Paulo (USP); Sch Med Wuerzburg; Fluorotronics Inc; Universidade Federal de São Paulo (UNIFESP)Isotretinoin is the drug of choice for the management of severe recalcitrant nodular acne. Nevertheless, some of its physical-chemical properties are still poorly known. Hence, the aim of our study consisted to comparatively evaluate the particle size distribution (PSD) and characterize the thermal behavior of the three encapsulated isotretinoin products in oil suspension (one reference and two generics) commercialized in Brazil. Here, we show that the PSD, estimated by laser diffraction and by polarized light microscopy, differed between the generics and the reference product. However, the thermal behavior of the three products, determined by thermogravimetry (TGA), differential thermal (DTA) analyses and differential scanning calorimetry (DSC), displayed no significant changes and were more thermostable than the isotretinoin standard used as internal control.Thus, our study suggests that PSD analyses in isotretinoin lipid-based formulations should be routinely performed in order to improve their quality and bioavailability. (C) 2010 Elsevier B.V. All rights reserved.
- ItemSomente MetadadadosEffect of Ag addition on phase transitions of the Cu-22.26 at.%Al-9.93 at.%Mn alloy(Elsevier B.V., 2013-02-20) Silva, R. A. G. [UNIFESP]; Gama, S. [UNIFESP]; Paganotti, A. [UNIFESP]; Adorno, A. T.; Carvalho, T. M.; Santos, C. M. A.; Universidade Federal de São Paulo (UNIFESP); Univ Estadual PaulistaThe phase transitions that occur in the Cu-22.26 at.%Al-9.93 at.%Mn and Cu-22.49 at.%Al-10.01 at.%Mn-1.53 at.%Ag alloys after slow cooling were studied using differential scanning calorimetry at different heating rates, microhardness changes with temperature, magnetization changes with temperature, scanning electron microscopy and energy dispersion X-ray spectroscopy. the results indicated that the presence of Ag does not modify the transition sequence of Cu-Al-Mn alloy, introduces a new transition due to the (Ag-Cu)-rich precipitates dissolution at about 800K, and changes the mechanism of DO3 phase dissolution. This mechanistic change was analyzed and a sequence of phase transitions was proposed for the reaction. (C) 2013 Elsevier B.V. All rights reserved.
- ItemSomente MetadadadosEstudo comparativo da preparação de filmes de poliuretano comercial e sua caracterização química via análise térmica, visando sua aplicação como biomaterial(Universidade Federal de São Paulo, 2017-03-10) Massei, Mariana Gurgel Rodrigues [UNIFESP]; Mercuri, Lucildes Pita [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Polyurethane (referred to by the acronym PUR) is a polymer comprising a chain of organic units linked by urethane bonds. This material is widely used in rigid and flexible foams, durable elastomers, high performance adhesives, sealants, fibers and biocompatible materials. These various applications can be attributed to the manner in which the synthesis is performed, i.e. by varying the monomers for the constitution of the polymer and reagents. The PUR monomer is isocyanate, which can be used in two forms: aromatic and aliphatic. Aromatics are the most used because they are more reactive and have lower cost, besides having greater stability and resistance. If the PURs are processed improperly they can generate products dangerous to health. From the preparation of the desired material will be carried out the study of this polymer aiming its application in several areas, due to its biocompatibility that is already well studied and published in the scientific literature. This work has as main objective to study the thermal behavior and the chemical and physicochemical characterization of the synthetic polyurethane films obtained by the solubility of this polymer in different solvents. For this, the following analytical, physical and physico-chemical techniques were used: Elementary analysis (AE), Thermogravimetry / Thermogravimetry (TG / DTG), Differential Exploration Calorimetry (DSC) and Fourier Transform Infrared Spectroscopy FTIR), X-ray diffractometry (XRD), Proton nuclear magnetic resonance (NMR-H1), UV-Vis spectrophotometry), Gel permeation chromatography (GPC) and RAMAN spectroscopy. Based on the results obtaine it was possible to evaluate that the PUR films (A, B and C) presented similar chemical and physicochemical characteristics. However, the profiles observed in the TG / DTG and DSC curves of the PUR-A films presented different thermal behavior, whereas the PUR-B (B; B1, B2, B3 and B4) and PUR-C (C3 and C4 ) Presented similar thermal behavior to their peers, respectively. The XRD data showed the efficiency of the chosen solvent by modifying the amorphous material with the presence of crystallites in the nonhomogeneous material. The obtained results were complementary and helped in the general characterization and discussion of the chosen techniques.
- ItemAcesso aberto (Open Access)Stability evaluation of tocopheryl acetate and ascorbyl tetraisopalmitate in isolation and incorporated in cosmetic formulations using thermal analysis(Universidade de São Paulo, Faculdade de Ciências Farmacêuticas, 2010-03-01) Almeida, Mariana Mandelli de; Lima, Cibele Rosana Ribeiro de Castro; Quenca-guillen, Joyce Santos; Moscardini Filho, Elder [UNIFESP]; Mercuri, Lucildes Pita [UNIFESP]; Santoro, Maria Inês Rocha Miritello; Kedor-hackmann, Erika Rosa Maria; University of São Paulo Faculty of Pharmaceutical Sciences Pharmacy Department; Universidade Federal de São Paulo (UNIFESP)In view of the increase in the number of cosmetic preparations containing antioxidant vitamins, chiefly, due to their action in preventing the process of skin aging, there is a need to develop pre-formulation studies and to validate analytical methods in order to obtain high quality products. Thus, the objective of this research was to evaluate and compare the thermal behavior of tocopheryl acetate and ascorbyl tetraisopalmitate as raw materials, and incorporated into a base cream. Thermogravimetry (TG / DTG) and differential scanning calorimetry (DSC) were used for this purpose. Both vitamins were found to be stable up to 250ºC. The base cream (placebo) and the sample (base cream containing the vitamins) presented different weight loss. Thermal analysis has shown itself to be an excellent tool for the characterization of these vitamins and can be used in routine analysis for quality control of this type of cosmetic formulation.
- ItemAcesso aberto (Open Access)Thermal behavior and decomposition kinetics of rifampicin polymorphs under isothermal and non-isothermal conditions(Universidade de São Paulo, Faculdade de Ciências Farmacêuticas, 2010-06-01) Alves, Ricardo; Reis, Thaís Vitória Da Silva; Silva, Luis Carlos Cides Da; Storpírtis, Silvia; Mercuri, Lucildes Pita [UNIFESP]; Matos, Jivaldo Do Rosário; University of São Paulo Faculty of Pharmaceutical Sciences Department of Pharmacy; Oswaldo Cruz Faculties; University of São Paulo Institute of Chemistry Department of Fundamental Chemistry; Universidade Federal de São Paulo (UNIFESP)The thermal behavior of two polymorphic forms of rifampicin was studied by DSC and TG/DTG. The thermoanalytical results clearly showed the differences between the two crystalline forms. Polymorph I was the most thermally stable form, the DSC curve showed no fusion for this species and the thermal decomposition process occurred around 245 ºC. The DSC curve of polymorph II showed two consecutive events, an endothermic event (Tpeak = 193.9 ºC) and one exothermic event (Tpeak = 209.4 ºC), due to a melting process followed by recrystallization, which was attributed to the conversion of form II to form I. Isothermal and non-isothermal thermogravimetric methods were used to determine the kinetic parameters of the thermal decomposition process. For non-isothermal experiments, the activation energy (Ea) was derived from the plot of Log β vs 1/T, yielding values for polymorph form I and II of 154 and 123 kJ mol-1, respectively. In the isothermal experiments, the Ea was obtained from the plot of lnt vs 1/T at a constant conversion level. The mean values found for form I and form II were 137 and 144 kJ mol-1, respectively.