ResumoA grande propagação da nanotecnologia nos tempos atuais requer estudos cada vez mais específicos para entender a evolução desses materiais. A obtenção de boas propriedades em nanocompósitos polímero/argila faz com que estudos mais aprofundados sejam realizados sobre a estabilidade térmica dos surfactantes nas temperaturas de processamento destes materiais. Neste trabalho, a estabilidade térmica de quatro sais quaternários de amônio, tais como brometo de hexadeciltrimetil amônio, cloreto de alquildimetilbenzil amônio, cloreto de estearildimetil amônio e cloreto de hexadeciltrimetil amônio foi avaliada, visando sua posterior intercalação em argilas bentoníticas nacionais, com o propósito de torná-las organofílicas para uso em nanocompósitos poliméricos. Os sais foram caracterizados termicamente por calorimetria exploratória diferencial e termogravimetria sob Ar e N 2 . Os resultados indicaram que os sais à base do ânion cloreto se degradaram em temperaturas similares e o sal à base do ânion brometo se degradou em temperatura superior. Além disso, este estudo indicou que o sal cloreto de estearildimetil amônio provavelmente terá sucesso na utilização como surfactante para o uso em nanocompósitos. Palavras-chave: nanocompósitos, argilas organofílicas, sais quaternários de amônio, estabilidade térmica. AbstractThe large propagation of nanotechnology in modern times requires more studies to meet their specific development. For
Studies of degradation have verified that the decomposition of some quaternary ammonium salts can begin to be significant at the temperature of about 180 ° C and like most thermoplastics are processed at least around this temperature, the thermal stability of the salt in clay should always be considered. Some salts are more stable than others, being necessary to study the degradation mechanisms of each case. In this work, four quaternary ammonium salts were characterized by differential scanning calorimetry (DSC) and thermogravimetry (TG). The results of DSC and TG showed that the salts based chloride (Cl-) anion begin to degrade at similar temperatures, while the salt based bromide (Br-) anion degrades at higher temperature. Subsequently, a quaternary ammonium salt was chosen to be used in organoclays, depending on its chemical structure and its thermal behavior.
Membranes can be defined as polymer film that acts as a semipermeable barrier to filtration in a molecular scale, separating two phases. In this work, microporous membranes were obtained from hybrid organic/inorganic polyamide66 (PA66) and clay mineral from Paraíba State, treated with a quaternary ammonium salt in order to make it organophilic. The membranes in the form of thin films were prepared by immersion-precipitation technique from the nanocomposites obtained by solution, with a pre-determined reaction time of 2 h, with characteristics suitable to be used in microfiltration process for separation of the oil present in water. Samples of natural and organophilic clay were characterized by X-ray fluorescence (XRF) and Fourier transform infrared spectroscopy (FTIR). Meanwhile, the membranes were characterized by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results of FRX and FTIR confirmed the presence of quaternary ammonium salt in the clay structure after treatment with organic salt. Through DSC analysis it was observed almost no change in the melting temperature of the pure polyamide66 membranes. By SEM, it was revealed an asymmetric morphology consisting of a skin layer and a porous sublayer, showing the pore size distribution appropriated to water-oil separation.
Paraíba is the main natural bentonite producing state of Brazil. Besides the advantage of abundance of bentonite clays, its transformation in organoclay is a simple method and there is only little study about the commercialization of Brazilian organoclays. In this work, Brazilian bentonite clay was organophilized with different quantity of a quaternary ammonium salt, such as 100, 125 and 150 wt.% in relation to Cationic Exchange Capacity (CEC) of the clay. The clays were characterized by X-ray Fluorescence (XRF), X-ray Diffraction (XRD), Thermogravimetry (TG) and Nuclear Magnetic Resonance (NMR). It was observed that with increasing amount of salt the degree of dispersion of the clay increased, leading in some cases to the delamination of the clay layers and its loss of thermal stability.
Considerando que o Brasil possui uma ampla área territorial, associada a grandes variações de temperatura, e que a junção desses fatores dificulta muito o transporte de medicamentos sensíveis à temperatura, o objetivo deste estudo é descrever, recorrendo à revisão de literatura, as boas práticas na logística de medicamentos, com ênfase nas vacinas. Este artigo consiste em estudo exploratório, descritivo, de revisão integrativa da literatura sobre a importância da aplicação das boas práticas de produtos biológicos, com ênfase no transporte de vacinas. A buscas de referências foi realizada nas bases de dados Biblioteca Virtual de Saúde, PubMed®, SciELO, Science Direct e LILACS. Os estudos demonstram que as vacinas, produtos perecíveis provenientes de antígenos, degradam-se e perdem a potência quando expostas a temperaturas fora dos limites de especificação. Por isso, o armazenamento e o transporte de vacinas é motivo de preocupação em várias organizações internacionais. Pode-se observar que o transporte logístico ainda precisa melhorar, tanto na área tecnológica quanto na operacional, por meio da capacitação contínua dos profissionais envolvidos e da participação de profissional farmacêutico, medidas que devem ser adotadas pelas empresas especializadas neste serviço.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.