Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-09-21T17:25:16Z No. of bitstreams: 1 NayaraCruz.pdf: 2821867 bytes, checksum: 4cc762016119d71d331457a53080cac3 (MD5) / Made available in DSpace on 2017-09-21T17:25:16Z (GMT). No. of bitstreams: 1 NayaraCruz.pdf: 2821867 bytes, checksum: 4cc762016119d71d331457a53080cac3 (MD5) Previous issue date: 2017-07-14 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The crystals based in Amino acid have been studied recently, mainly due to their useful properties for electronic, non-linear optical and magnetic applications. One of most used amino acids are β-alanine, whose complexes with nickel were studied in the 1990s. However, there are no studies on the thermal and structural stability of this material. In order to better investigate β-alanine complexes with metal ions, this work presents the structural and thermal study of nickel (II) β-alaninate crystal. The crystals were grown by slow evaporation of the solvent. The crystals grew after a period of 30 days. The techniques used for the characterization of the sample were: X-Ray Diffraction (XRD) along with the refinement by the Rietveld method, Raman spectroscopy at room temperature and with temperature variation, Fourier Transform Infrared Spectroscopy (FTIR) and Thermal Analysis By Differential Exploratory Calorimetry (DSC). The XRD data showed that the crystals grown were the desired ones, presenting the same triclinic structure and spatial group P1. The DSC results showed events corresponding to water loss followed by phase transformation and subsequent melting at approximately 138 ° C. The results obtained by Raman Spectroscopy at room temperature and with temperature variation showed 32 spectral bands for the crystal, of which 5 are referring to the network modes or external modes. Raman spectroscopy confirmed the observed phase transformation on the DSC curve due to the loss of the water molecule. As the temperature increases, the bands shift to the number of smaller waves. For the results obtained at temperatures above 137 ° C the appearance of spectral bands was not observed, indicating that the crystal was melted as observed in the DSC curve. The results of X-ray diffraction as a function of temperature showed that, as the temperature increases, the peaks shift to smaller angles and that the process is non-reversible, characteristic of a phase transformation. For the FITR data we have that most bands have a high spectral absorption showing a total of 26 bands. The present result shows that the crystal is thermally stable up to 110 ° C and can be used for application below this temperature. / Cristais à base de aminoácidos têm sido estudados recentemente, principalmente devido à suas propriedades úteis para aplicações eletrônicas, óptica não linear e magnéticas. Dentre os aminoácidos mais utilizados há a β-alanina, cujos complexos com níquel foram estudados na década de noventa. Contudo, não há estudos da estabilidade térmica e estrutural desse material. No intuito de investigar melhor complexos de β-alanina com íons metálicos, este trabalho apresenta o estudo estrutural e térmico do cristal de β- alaninato de níquel (II). Os cristais foram crescidos por meio do método de evaporação lenta do solvente. Os cristais cresceram após um período de 30 dias. As técnicas utilizadas para a caracterização da amostra foram: Difração de Raios X (DRX) juntamente com o refinamento pelo método de Rietveld, Espectroscopia Raman em temperatura ambiente e com variação de temperatura, Espectroscopia no Infravermelho com Transformada de Fourier (FTIR) e Análise Térmica pela técnica de Calorimetria Exploratória Diferencial (DSC). Os dados de DRX comprovaram que os cristais crescidos eram os desejados, apresentando a mesma estrutura triclínica e grupo espacial P1. Os resultados de DSC mostraram eventos que correspondem à perda de água seguida da transformação de fase e posterior fusão em aproximadamente 138°C. Os resultados obtidos por Espectroscopia Raman à temperatura ambiente e com variação de temperatura apresentaram 32 bandas espectrais para o cristal, das quais cinco são referentes aos modos de rede ou modos externos. A espectroscopia Raman confirmou a transformação de fase observada na curva de DSC, devido à perda da molécula de agua. À medida que a temperatura aumenta, ocorreu o deslocamento das bandas para número de ondas menores. Para os resultados obtidos em temperaturas superiores a 137°C não se observou o aparecimento de bandas espectrais, indicando que o cristal sofreu fusão conforme observado na curva de DSC. Os resultados de Difração de Raios X em função da temperatura mostraram que, à medida que ocorre o aumento da temperatura ocorre o deslocamento dos picos para ângulos menores e que o processo é não reversível, característica de uma transformação de fase. Para os dados de FITR, a maioria das bandas apresentam uma alta absorção espectral mostrando um total de 26 bandas. O presente resultado mostra que o cristal é termicamente estável até 110°C podendo ser utilizado para aplicação abaixo dessa temperatura.

<p>Polymers are subjected to physical and chemical changes during their processing, service life, and further recovery, and they may also interact with impurities that can alter their composition. These changes substantially modify the stabilisation mechanisms and mechanical properties of recycled polymers. Detailed knowledge about how the different stages of their life cycle affect the degree of degradation of polymeric materials is important when discussing their further waste recovery possibilities and the performance of recycled plastics. A dual-pronged experimental approach employing multiple processing and thermo-oxidation has been proposed to model the life cycle of recycled high-impact polystyrene (HIPS). Both reprocessing and thermo-oxidative degradation are responsible for coexistent physical and chemical effects (chain scission, crosslinking, apparition of oxidative moieties, polymeric chain rearrangements, and physical ageing) on the microstructure and morphology of polybutadiene (PB) and polystyrene (PS) phases; these effects ultimately influence the long-term stability, and the rheological and mechanical behaviour of HIPS. The PB phase has proved to be the initiation point of HIPS degradation throughout the life cycle. Thermo-oxidation seems to have more severe effects on HIPS properties; therefore, it can be concluded that previous service life may be the part of the life cycle with the greatest influence on the recycling possibilities and performance of HIPS recyclates in second-market applications. The results from the life cycle degradation simulation were compared with those obtained from real samples from a large-scale mechanical recycling plant. A combination of different analytical strategies (thermal analysis, vibrational spectroscopy, and chromatographic analysis) is necessary to obtain a detailed understanding of the quality of recycled HIPS as defined by three key properties: degree of mixing, degree of degradation, and presence of low molecular weight compounds.</p>

Polymers are subjected to physical and chemical changes during their processing, service life, and further recovery, and they may also interact with impurities that can alter their composition. These changes substantially modify the stabilisation mechanisms and mechanical properties of recycled polymers. Detailed knowledge about how the different stages of their life cycle affect the degree of degradation of polymeric materials is important when discussing their further waste recovery possibilities and the performance of recycled plastics. A dual-pronged experimental approach employing multiple processing and thermo-oxidation has been proposed to model the life cycle of recycled high-impact polystyrene (HIPS). Both reprocessing and thermo-oxidative degradation are responsible for coexistent physical and chemical effects (chain scission, crosslinking, apparition of oxidative moieties, polymeric chain rearrangements, and physical ageing) on the microstructure and morphology of polybutadiene (PB) and polystyrene (PS) phases; these effects ultimately influence the long-term stability, and the rheological and mechanical behaviour of HIPS. The PB phase has proved to be the initiation point of HIPS degradation throughout the life cycle. Thermo-oxidation seems to have more severe effects on HIPS properties; therefore, it can be concluded that previous service life may be the part of the life cycle with the greatest influence on the recycling possibilities and performance of HIPS recyclates in second-market applications. The results from the life cycle degradation simulation were compared with those obtained from real samples from a large-scale mechanical recycling plant. A combination of different analytical strategies (thermal analysis, vibrational spectroscopy, and chromatographic analysis) is necessary to obtain a detailed understanding of the quality of recycled HIPS as defined by three key properties: degree of mixing, degree of degradation, and presence of low molecular weight compounds. / QC 20101119