DANAE LOPES FRANCISCO
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Artigo IPEN-doc 27595 Noncovalently functionalized halloysite nanotubes for use in reinforced polymer composites2020 - FRANCISCO, DANAE L.; PAIVA, LUCILENE B.; ALDEIA, WAGNER; LUGAO, ADEMAR B.; MOURA, ESPERIDIANA A.B.The inorganic halloysite nanotube (HNT) is a promising type of naturally occurring fillers with many important uses in different fields. An HNT has a relatively low content of hydroxyl groups on its surface, which makes it relatively hydrophobic, although this is not always sufficient to guarantee good interfacial adhesion in composite systems. Further surface treatment is required to improve the compatibility of HNTs with polymer matrixes, maximizing interfacial interactions. The aim of the present work was to study a noncovalent functionalization of halloysite with 2,2′-(1,2-ethenediyldi-4,1-phenylene) bisbenzoxazole (EPB), based on electron transfer, for further use of EPB as a coupling agent in polymer/HNT compatibility. A set of characterization techniques were performed to evaluate the chemical and physical properties and evidence the functionalization. The results revealed the surface modification of halloysite upon functionalization. Emphasis was for powder wettability by tensiometry based on Washburn because no studies about halloysite powders using this technique could be found in the literature. The results demonstrate a reduction in the total surface energy of the system, usually accompanied by a reduction in the polar component upon HNT modification.Artigo IPEN-doc 25303 Caracterização de nanotubos de haloisita funcionalizados covalentemente para aplicação em compósitos de matriz polimérica2018 - FRANCISCO, D.L.; SILVA, F.A.; PAIVA, L.B.; ALDEIA, W.; LUGAO, A.B.; MOURA, E.A haloisita (HNT) possui interessantes características suscitando seu interesse como candidata à produção de nanocompósitos poliméricos de alto desempenho. O teor relativamente baixo de grupos hidroxílicos em sua superfície a torna relativamente hidrofóbica, embora, às vezes, isso não seja suficiente para garantir uma boa adesão interfacial com a matriz polimérica. Sendo então, necessário um tratamento hidrofóbico adicional para favorecer a compatibilidade com a matriz. No presente estudo, um tratamento hidrofóbico da HNT foi avaliado a partir de soluções hidrolisadas de 3-(trimetoxisilil)propil metacrilato (MAPTS) em meio alcoólico. A HNT modificada foi caracterizada através da análise de área superficial específica, análise termogravimétrica e ensaio de extração em solução de água/tolueno. Os resultados mostraram uma redução na área superficial, um aumento na perda de massa final no ensaio termográvimetrico e um deslocamento da HNT modificada para o tolueno, evidenciando a funcionalização da HNT com o MAPTS.Capítulo IPEN-doc 24662 Characterization of non-covalently functionalized halloysite2018 - FRANCISCO, DANAE L.; PAIVA, LUCILENE B. de; ALDEIA, WAGNER; LUGAO, ADEMAR B.; MOURA, ESPERIDIANA A.B.The inorganic nanotube halloysite (HNT) is a promising type of natural occurring filler for polymers. Its characteristics, such as high aspect ratio (10–50), small size, and high strength (elastic modulus—140 GPa) suggest that HNTs have a potential use in high-performance polymer nanocomposites. Compared to other nanoclays and nanosilica the relatively low content of hydroxyl groups on their surfaces makes HNTs relatively hydrophobic, although, sometimes, this is not sufficient for guaranty a good interfacial adhesion in composite systems. Further hydrophobic treatment is required to improve HNTs compatibility with polymer matrixes, maximizing interfacial interactions. In the present study, different percentages of EPB (2,2-(1,2-ethene diyldi-4,1-phenylene) bisbenzoxazole) was used to perform a non-covalent functionalization of halloysite, based on electron transfer interactions. The functionalization is characterized by specific surface area (BET), thermogravimetric analysis (TG) and water/toluene extraction experiment.