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Master's Dissertation
DOI
10.11606/D.88.2012.tde-13042012-150532
Document
Author
Full name
Patricia Coelho Lombardo
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2012
Supervisor
Committee
Cavalheiro, Carla Cristina Schmitt (President)
Chinelatto, Marcelo Aparecido
Goi, Beatriz Eleuterio
Title in Portuguese
Fotooxidação do compósito poli (óxido de etileno)/Montmorilonita: influência da argila e de fotoestabilizantes
Keywords in Portuguese
Compósitos
Degradação fotooxidativa
Estabilizantes
Montmorilonita
Poli(óxido de etileno)
Abstract in Portuguese
Compósitos de Poli (óxido de etileno) (PEO) com diferentes concentrações de argila montmorilonita SWy-1 foram preparados pelo método de intercalação em solução. Os filmes obtidos foram caracterizados por difração de raios X (DRX), microscopia eletrônica de varredura (MEV) e espectrocopia de infravermelho com transformada de Fourier (FTIR). Os resultados de DRX mostraram que os compósitos obtidos foram do tipo intercalados. As imagens de MEV indicaram a existência de agregados de argila SWy-1 dispersos na matriz polimérica. A influência da argila na estabilidade térmica e na cristalização do PEO foi estudada por termogravimetria (TG) e calorimetria exploratória diferencial (DSC). As curvas TG mostraram que a temperatura inicial de degradação térmica (Ti) diminui com o aumento da concentração de SWy-1. Além disso, uma pequena diminuição na amplitude do pico de fusão do PEO foi observado nos resultados de DSC. Os filmes de PEO e dos compósitos de PEO/SWy-1 foram irradiados com luz UV e a fotooxidação foi acompanhada por cromatografia de exclusão por tamanho (SEC). Os resultados de SEC mostraram que a taxa de oxidação do PEO puro foi mais rápida em comparação aos compósitos de PEO/SWy-1. Nesse caso a argila pode ser considerada como um estabilizante contra a irradiação UV. O efeito de estabilizantes do tipo absorverdores de UV (moléculas derivadas da 2-hidroxibenzofenona) e do tipo HALS (Tinuvin 770), quando adicionados ao PEO e ao compósito de PEO/SWy-1, também foi analisado por SEC após a fotooxidação dos filmes. Os resultados mostraram que a adição do estabilizante Tinuvin 770 proporcionou maior estabilidade a matriz polimérica durante o processo degradativo, comparado ao estabilizante 2-hidroxibenzofenona.
Title in English
Photo-oxidation of poly (ethylene oxide)/Montmorillonite composites: influence of the clay and photostabilizers
Keywords in English
Composites
Montmorillonite
Photo-oxidative degradation
Poly (ethylene oxide)
Stabilizers
Abstract in English
Poly(ethylene oxide) (PEO) composites with different concentrations of SWy-1 montmorillonite clay were prepared by solution intercalation method. The thin films obtained were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The XRD results showed that the composites obtained were of the type intercalated. The SEM images have indicated that there are SWy-1 clay aggregates scattered in the polymer matrix. The influence of clay on thermal stability, melting and polymer crystallization processes was studied by thermogravimetric analysis (TG) and differential scanning calorimetric (DSC). The TG curves showed that the initial thermal degradation temperature (Ti) decrease with increasing concentration of SWy-1. Besides, a small decrease in the amplitude of the melting peak of PEO was observed in the DSC results. The thin films of PEO and PEO/SWy-1 composites were exposed to UV irradiation and the photodegradation was accompanied by size exclusion chromatography (SEC). The SEC results showed that the rate of oxidation of pristine PEO was faster compared to PEO/SWy-1 composites. In this case the clay can be considered as a stabilizer against UV irradiation. The effect of UV absorbers (2-hydroxybenzophenone derivated molecules) and HALS (Tinuvin 770) stabilizers, when added to PEO and PEP/SWy-1 composites, also were studied by SEC after the thin films photodegradation. The results allowed to conclude that the polymer matrix became more stable for degradation with adition of Tinuvin 770 stabilizer when compared to 2-hydroxybenzophenone.
 
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Publishing Date
2012-08-03
 
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