Gilmar Trindade de Araújo

Study of the effects of acetylation treatments on sisal fiber.

The use of vegetable fibers in composites is highly viable regarding about the use of materials from renewable sources, the biodegradability and the socioeconomic advantages in the production of raw vegetable. The sisal fibers are highly hygroscopic and this is a main problem in the production of composites, inducing dimensional changes under moisture influence, deposition of the matrix products and degradation. The treatment of the acetylation was applied at different temperatures and reaction times, and the efficiency of treatments, considering the reduction of the hydrophilicity and maintenance of the mechanical properties, was evaluated by water sorption, mechanical properties and the infrared spectroscopy. With acetylation the fibers had weight reductions for water sorption up to 50% compared to untreated. The treatments for 3 h decreased the mechanical properties while the 120 °C for 1 h showed better physico-mechanical properties and increase of apolar groups.

Tratamento do efluente do biodiesel utilizando a eletrocoagulação/flotação: investigação dos parâmetros operacionais

Electrocoagulation/flotation process was applied to treat biodiesel wastewater using aluminium electrodes. Firstly, a literature survey was conducted to choose the process variables and then, operational parameters including initial pH, electrode distance and reaction time were tested. Experimental results showed the best parameter that can be used in a factorial design for further studies. The results indicate that electrocoagulation/flotation is very efficient to reduce oil and grease, the effluent was very clear after treatment and small amount of sludge was produced.

Avaliação dos efeitos da acetilação nas propriedades das fibras de caroá

Fiber plants are highly hygroscopic and this feature appears as a major problem in its applicability to production of cement composites, inducing dimensional changes under the moisture influence, deposition of the matrix products and degradation. To find alternatives to minimize the problems in cementitious composites with respect to Neoglaziovia variegata fibers, it was aimed in this study to evaluate the application of the treatment of acetylation at different levels. Their efficiency was determined by reduction of hydrophilicity, maintaining the mechanical performance of fibers, and changes in chemical composition, measured through the physical, chemical, mechanical and thermal properties. The acetylation at 120 °C and/or 3 h showed reductions of 42 to 47% in hydrophilicity. In the acetylation at 120 °C for 1 h, the increase in mechanical properties was more than 110%. The treatment also changed the composition of the fibers with the introduction of acetyl groups, increased the thermal stability and reduced the crystallinity of cellulose, without degradation in its surface of adhesion.

Modificação das propriedades das fibras de curauá por acetilação

In cementitious composite the vegetable fibers may suffer various degrees of degradation when exposed to alkaline medium. The alkaline degradation of macromolecular components of fibers mainly by lignin solubilization and cellulose defibrillation, compromising the physical and mechanical properties. The resistance of plant fiber to alkali attack can be improved by chemical surface treatments such as acetylation that can reduce the hygroscopic nature of lignocellulosic introducing hydrophobic functional groups in its chemical structure. Thus, the aim of this study was the application of the acetylation treatment at different levels to improve the durability of the fibers.The acetylation treatment in curaua fiber was applied at different temperatures and reaction times, and its efficiency, considering the reduction of hydrophilicity and maintenance of the physical-mechanical performance of fibers was evaluated by water absorption, mechanical resistance, infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis and diffraction of x-rays. When acetylated curaua fibers absorbed up to 55% less water than untreated fibers. In strength, losses were up 52%. The acetylation treatment introduced hydrophobic chemical groups in the composition and changed crystalline character of fibers.

Influência da temperatura de secagem em leito de jorro sob as características físico-químicas do repolho roxo

O repolho e uma hortalica folhosa com grande valor nutritivo e poder antioxidante, porem rapidamente deteriora-se pelo elevado teor de agua. O processo de desidratacao de polpa ou pure de frutas e hortalicas tem sido amplamente empregado, devido a preservacao das qualidades nutricionais e por sua vez, a secagem em leito de jorro vem sendo amplamente utilizada por atender principalmente esse requisito. Embora os resultados relativos a qualidade dos pos, indiquem a viabilidade do leito de jorro, faz-se necessarios estudar qual a influencia da temperatura nas caracteristicas fisico-quimicas do po obtido. Tendo em vista todos os argumentos mostrados, o presente trabalho tem como objetivo estudar a influencia da temperatura do leito de jorro nas caracteristicas fisico-quimicas do repolho roxo. Primeiramente foi obtido o sumo e a caracterizacao fisico-quimico do mesmo, em seguida o mesmo foi desidratado em leito de jorro nas temperaturas de 60, 70 e 80 °C e posteriormente os pos obtidos foram submetidos a avaliacao fisico-quimica: atividade de agua, teor de agua, pH, acidez total titulavel, teor de solidos soluveis (°Brix) e cor. Os valores de atividade de agua e acidez diminuiram com o aumento da temperatura ocorrendo o inverso para os outros parâmetros. Sendo verificada uma influencia significativa da temperatura sob os parâmetros fisico-quimicos. Influence of drying temperature in spouted bed under the physicochemical characteristics of red cabbage Abstract: Cabbage is a leafy vegetable with high nutritional value and antioxidant power, but quickly deteriorates because of the high water content. The pulp or mashed fruits and vegetables dehydration process has been widely used due to preservation of nutritional quality, and in turn, the drying in spouted bed has been widely used to cater mainly this requirement. Although the results on the quality of post indicate the feasibility of the spouted bed, it is necessary to study the influence of temperature on the physicochemical characteristics of the resulting powder. In view of all arguments shown, the present work aims to study the influence of the spouted bed temperature on the physicochemical characteristics of the purple cabbage. First was obtained juice and physicochemical characterization of it, then it was dried in spouted bed at temperatures of 60, 70 and 80 ° C and then the powders were subjected to physicochemical evaluation: water activity , water content, pH, titratable acidity, soluble solids (° Brix) and color. The water activity and acidity values decreased with increasing temperature, the opposite occur for the other parameters. It is verified a significant influence of temperature on the physical and chemical parameters.