Encapsulamento de solventes em nanotubos de haloisita para promoção de auto-reparo em polímeros

Micro cracking during service is a critical problem in polymer structures and polymer composite materials. Self-healing materials are able to repair micro cracks, thus their preventing propagation and catastrophic failure of structural components. One of the self-healing approaches presented in the literature involves the use of solvents which react with the polymer. The objective of this research is to investigate a procedure to encapsulate solvents in halloysite nanotubes to promote self-healing ability in epoxy. Healing is triggered by crack propagation through embedded nanotubes in the polymer, which then release the liquid sovent into the crack plane. Two solvents were considered in this work: dimethylsulfoxide (DMSO) and nitrobenzene. The nanotubes were coated using the layer-by-layer technique of oppositely charged polyelectrolytes: cetyltrimethylammonium bromide (CTAB) and sodium polyacrylate. Solvent encapsulation was verified by X-ray diffraction (XRD), Fourier transform infrared (FTIR), analysis thermogravimetry (TGA), adsorption and desorption of nitrogen and scanning electron microscopy (SEM). The introduction of the solvent DMSO into the cavity of the nanotubes was confirmed by the techniques employed. However, was not verified with nitrobenzene only promoted clay aggregation. The results suggest that the CTAB reacted with the halloystite to form a sealing layer on the surface of the nanotubes, thus encapsulating the solvent, while this was not verified using sodium polyacrylate.

Utilização do controle estatístico do processo para monitoramento do peso médio de cápsulas de Tuberculostáticos: estudo de caso no NUPLAM- RN

This Master Thesis presents a case study on the use of Statistical Process Control (SPC) at the Núcleo de Pesquisas em Alimentos e Medicamentos (NUPLAM). The SPC basic tools have been applied in the process of the tuberculostáticos drugs encapsulation, primarily concerning the objective to choose, between two speeds, which one is the best one to perform the tuberculostatics encapsulation. Later on, with the company effectively operating, the SPC was applied intending to know the variability of the process and, through the tracking of the process itself, to arrive at an estimated limit for the control of future lots of tuberculostatics of equal dosage. As special causes were detected acting in the process, a cause-and-effect diagram was built in order to try to discover, in each factor that composes the productive process, the possible causes of variation of the capsules average weight. The hypotheses raised will be able to serve as a base for deepened the study to eliminate or reduce these interferences in the process. Also a study on the capacity of the process to attend the specifications was carried out, and this study has shown the process´s inaptitude to take care of them. However, on the side of NUPLAM exists a real yearning to implant the SPC and consequently to improve the existing quality already present on its medicines

Referenciação anáforica: um estudo de produções textuais no ensino fundamental

Esta pesquisa trata da referenciação ocorrida pelas anáforas diretas e indire-tas em produções textuais de alunos do Ensino Fundamental. Como elemento pri-mordial de nossas investigações, ancoramo-nos na referenciação e estudos da aná-fora no âmbito da Lingüística Textual como fazem Mondada e Dubois (2003); KOCH (2003) e Marcuschi (2005). De acordo com estudos já realizados e envolvidos com a temática, defendemos a noção de referenciação como sendo um processo de cons-trução de sentidos que se realiza no discurso, isto é, em atividades interativas entre os sujeitos exigindo, portanto, uma ação colaborativa entre os interlocutores. Nesse aspecto, a interação precisa existir, visto que os referentes de um termo anafórico nem sempre se encontram na superfície textual; muitas vezes, são construídos a partir de uma representação ou modelo mental disponível na memória discursiva. Nessa perspectiva, procuramos analisar o processo de referenciação construído a partir de anáforas diretas e indiretas identificando as estratégias utilizadas em textos produzidos em situações de sala de aula. Dizemos que a anáfora direta, de modo geral, é definida pela relação de correferencialidade estabelecida entre o anafórico e seu antecedente, enquanto a anáfora indireta é vista como uma estratégia referenci-al de associação, sem referente explícito, tendo que se esforçar para estabelecer a continuidade referencial no texto e para isso utiliza-se da ativação (referenciação mental) de elementos novos e não de uma reativação de referentes já conhecidos, o que constitui um processo de referenciação implícita. Para alcançarmos nosso obje-tivo, utilizamos como subsídio teórico, o processo de informação na memória cogni-tiva, a referência e estudos da anáfora no âmbito da Lingüística Textual. O corpus deste trabalho constitui-se de sessenta textos escritos por alunos de 7ª série (atual 8º ano), dentre os quais analisamos o processo de referenciação ocasionado pelas anáforas diretas e indiretas em doze desses textos. Considerando os dados analisa-dos, dentre os tipos de anáforas estudados, constatamos que houve preponderância no uso das anáforas diretas, destacando-se entre elas a anáfora direta correferencial co-significativa, com maior manifestação no uso das retomadas diretas por pronomi-nalização

Preparação de resinas de poliuretana à base de óleo de mamona e dietanolamina

The aim of this work was the preparation of polyols from reactions between castor oil and dietanolamine to increase the hydroxyl content and the network degree in the products to application in electronic devices. The polyols and the mixtures obtained were characterized by nuclear magnetic ressonance. Castor oil (CO) is a natural triglyceride - based polyol possessing hydroxyl groups, which allow several reactions that produce many different products. Among them are the polyurethanes (PU), which have been considered an ideal product for the covering of electricelectronic circuits, due to their excellent electrical, shock-absorbing, solvents resistance and hydrolytic stability properties. About 90% of the fatty acids present in the castor oil are ricinoleic acid (12-hydroxyoleic acid), while the remaining 10% correspond to non-hydroxylated fatty acids, mainly linoleic and oleic acids. The chemical analysis of castor oil indicates a hydroxyl number of 2.7. In this work, a polyol was obtained by the reaction of the CO with diethanolamine (DEA), in order to elevate the hydroxyl value from 160 to 230 or to 280 mgKOH/g, and characterized by nuclear magnetic resonance (NMR) 1H and 13C (Mercury 200). The polyadition of the resulting polyol with isophorone diisocianate (IPDI) was carried out at 60°C, and the reaction kinetics was followed by rheological measurements in a Haake RS150 rheometer. The electrical properties were determined in a HP LCR Meter 4262A, at 1.0 Hz and 10.0 KHz. The chemical analysis showed that the polyols obtained presented hydroxyl number from 230 to 280 mgKOH/g. The polyadition reaction with IPDI produced polyurethane resins with the following properties: hardness in the range from 45 shore A to 65 shore D (ASTM D2240); a dielectric constant of 3.0, at 25°C (ASTM D150). Those results indicate that the obtained resins present compatible properties to the similar products of fossil origin, which are used nowadays for covering electric-electronic circuits. Therefore, the PUs from castor oil can be considered as alternative materials of renewable source, free from the highly harmful petroleum - derived solvents