No abstract

RESUMO A tecnologia de fabricação por filamento fundido (FFF) utilizando polímeros como PLA e ABS é bem conhecida. Contudo, o desenvolvimento de filamentos compósitos para esta tecnologia de manufatura aditiva, bem como a determinação dos parâmetros de processamento e das propriedades resultantes na extrusão e naimpressão 3D, ainda requerem pesquisa. Esse estudo exploratório analisa as propriedades químicas, térmicas e a morfologia de filamento de matriz polimérica de PLA e talos de tabaco, visando sua utilização no processo FFF. Os materiais utilizados foram talos de tabaco moídos e PLA. As partículas de tabaco, com tamanho médio de 50 ?m, apresentaram-se aleatoriamente distribuídas no filamento. No entanto, aglomerados de partículas, bolhas e porosidades foram observados no centro do filamento. Ensaios por espectroscopia no infravermelho por transformada de Fourier mostraram que o filamento compósito apresentou interação mecânica entre os materiais. A análise térmica permitiu verificar que não houve degradação do pó de talos de tabaco, mantendo a integridade química e física do filamento compósito a temperatura de extrusão de 180 °C. A calorimetria exploratória diferencial revelou que as partículas de pó de talos de tabaco podem ter atuado como agente nucleante, aumentando o grau de cristalinidade do filamento compósito. Sugere-se para estudos futuros o aumento do percentual de pó de talos de tabaco, a investigação de outros métodos de preparação de compósitos, bem como um estudo da adição de plastificantes ou agentes compatibilizantes para aprimorar a ligação entre a interface do PLA e as partículas de tabaco.

In this research, the combined effects of polydimethylsiloxane (PDMS) and different conditions of oxygen volumetric mass transfer coefficient (k(L)a) on lipase production by Staphylococcus warneri EX17 were studied and optimized in bioreactor cultures. Raw glycerol from biodiesel synthesis was used as the sole carbon source. Full-factorial central composite design and the response surface methodology were employed for the experimental design and analysis of the results. The optimal polydimethylsiloxane concentration and mass coefficient transfer (k(L)a) were found to be 13.5% (v/v) and 181 h(-1), respectively. Under these conditions, the maximal cell production obtained was 10.0 g/l, and the volumetric lipase activities of approximately 490 U/l, after 6 h of cultivation. These results are in close agreement with the model predictions. Results obtained in this work reveal the positive effects of PDMS on oxygen volumetric mass transfer coefficient (k(L)a) in the Staphylococcus warneri EX17 cultivation and lipase production.

The main objective of this study is to analyze the use of tobacco stalk to develop new composite materials. For this purpose, tests and analyses were carried out to characterize the morphological, thermal, and chemical properties, as well as to obtain structural information about this plant waste. Morphology was analyzed by scanning electron microscopy (SEM). Thermogravimetry (TGA) was used to analyze mass loss and temperature degradation. Fourier-transform infrared spectroscopy (FTIR) was applied to determine the chemical composition. SEM showed the presence of filling components such as parenchyma and vascular elements of the xylem. FTIR showed the presence of elements such as absorbed water and primary and secondary aliphatic alcohols identified in cellulose, hemicelluloses, lignin, and carboxylic acids, among other substances. TGA showed cellulose degradation temperature between 250 and 350 °C. The test results indicate that tobacco stalks can be used to develop composite materials as fillers.

BACKGROUND: In this study the effects of the addition of emulsified polydimethylsiloxane (PMDS) FG-10 on the oxygen transfer coefficient (k L a) of submerged cultures of Staphylococcus warneri EX17 and its lipase production is described. FG-10 is an emulsified silicone capable of dissolving 50 times more oxygen than water. The combined effects of FG-10 concentration and different conditions of agitation were optimized in bioreactors using statistical design tools, and the cultures were run using raw glycerol from biodiesel synthesis as the sole carbon source.