Leila Aparecida de Castro Motta

Efeito da aplicação do poliestireno sulfonado (PSSNa) como aditivo em argamassas e concretos de cimento Portland CPV32

In this work an investigation was made of the effects from adding PSSNa, obtained from disposable polystyrene (PS) cups, as admixture agent in mortars and concrete with varying ratios from 0.25 to 1.00%. The evaluation of PSSNa as additive was based on results of fluidity and mechanical strength to compression. In mortars with water/cement ratio of 0.48, an increase in flow was observed when the dosage of PSSNa varied from 0.25 to 1.00%. The dispersion of mortar components was improved due to the adsorption of PSSNa on cement particles, which increased the mechanical strength of mortars. Similar results were obtained with the application of PSSNa to concrete. The slump of the concrete taken as reference was 50 mm, while for the concrete with PSSNa it reached about 200 mm. Because of its plasticization of concrete, PSSNa can be used as additive to reduce the amount of water required. For instance, a concrete with the same slump of the reference concrete was produced using PSSNa and a reduction of 20.8% in the volume of water. The increase in mechanical strength was 21.5 and 26.3%, respectively, at 7 and 28 days of curing. These results showed that PSSNa solutions can act as superplasticizer or as admixture to reduce the amount water in mortars and concretes.

Painéis sanduíches de poliéster reforçado com fibras de rami para aplicação na Construção Civil

RESUMO Neste trabalho foram produzidos e caracterizados mecanicamente compositos de resina de poliester reforcada com tecido bidirecional de fios de rami, com diferentes teores de reforco. Estes compositos foram testados experimentalmente e numericamente como faces de paineis sanduiches formados com nucleos de bucha vegetal impregnada com resina de poliester e poliestireno expandido - EPS. A caracterizacao mecânica dos materiais em estudo foi realizada em laboratorio a partir de ensaios de tracao e flexao, e simulacao numerica pelo Metodo de Elementos Finitos (MEF). A microestrutura do composito foi analisada por Microscopia Eletronica de Varredura (MEV). A partir das propriedades mecânicas obtidas para os compositos reforcados com tecido bidirecional de fios de rami e nucleos de EPS e bucha vegetal, observou-se viavel a confeccao de paineis sanduiches para aplicacao na Construcao Civil. Os compositos com 50% de volume de fios de rami apresentaram as melhores propriedades mecânicas e foram usados como faces nos prototipos dos paineis. Os nucleos em estudo apresentaram bons resultados, com destaque para a bucha vegetal impregnada de resina poliester, que apresentou maior rigidez e opcoes de confeccao de paineis com maiores dimensoes e mais delgados. O presente trabalho evidenciou o potencial das fibras vegetais para uso como constituintes dos compositos polimericos e nucleo dos paineis sanduiches e, portanto, revela uma nova alternativa de aproveitamento dessas fibras para aplicacao no setor da construcao. ABSTRACT In this work, composites of polyester resin reinforced with ramie fiber bidirectional woven cloth in different content by volume have been produced and characterized. These composites were tested experimentally and numerically as faces of sandwiches panels with cores of sponge gourd impregnated with polyester resin and expanded polystyrene-EPS. Mechanical characterization of these materials was conducted in the laboratory from tensile and bending tests, and numerical simulation using Finite Element Method (FEM). The composite was analyzed by Scanning Electron Microscopy (SEM). The mechanical properties obtained for the composites and cores showed viable making sandwich panels for application in construction. The composites with 50% volume fibers presented the best mechanical properties and have been used as faces in prototypes of the panels. The cores in study showed good results, with emphasis on the sponge gourd impregnated with polyester resin, which showed the highest stiffness and making options with larger and thinner panels. The present study showed the potential of natural fibers for use as reinforcing of polymeric composites and sandwich panels cores and so a new alternative use of these fibers for applications in the construction.

USE OF LATEX IN CELLULOSE FIBERS AND REPLACEMENT WITH METACAULIM FOR APPLICATION IN COMPOSITES WITH CEMENT MATRIX

In this work, it was studied the addition of latex in cellulose pulps in cement matrices. It is known that the alkalinity of the matrix degrades the fiber. Therefore, in addition of latex in fiber, the alkalinity of the matrix was reduced by replacing part of the cement with metakaolin. The influence of the analyzed parameters (percentage of cellulose, the percentage of latex and percentage of metakaolin) on the mechanical and physical properties of the cement composites was evaluated through an experimental planning. From this planning, it was possible to develop a model of equations that optimized the results of the modulus of rupture and water absorption. Flexural strength and water absorption tests were made on composites at 28 days of age. It was observed that the best conditions analyzed to maximize the value of the rupture modulus was the combinations of the values of cellulose in 8.5%, of latex in the value of 0.249% and of metakaolin in the central point (19%), resulting in the value for rupture modulus of 14.5 MPa. Regarding the absorption, it was observed that only the cellulose variable was significant for this response. Higher concentrations of cellulose resulted in higher values for percentage of absorption, due to the hydrophilicity of the natural fiber.

Polymeric blends of hydrocolloid from chia seeds/apple pectin with potential antioxidant for food packaging applications

The aim of this study was to investigate the antioxidant, mechanical and physical properties of a new film-based polymeric blend of hydrocolloids obtained from the aqueous extraction of chia seeds (source antioxidants) and apple pectin. The individual matrices films were brittle and rigid with poor mechanical properties. The blends formulations contributed to improved mechanical properties regarding workability and resistance. The antioxidant results showed the potential hydrocolloid from chia seeds as natural source of antioxidant in these polymeric films. The formulation 3 (14(hydrocolloid):41(pectin):25(glycerol):20(glutaraldehyde) displayed well thermal, mechanical, morphological and antioxidant properties, suggesting their great potential for food packaging.