Andrea de Vasconcelos Ferraz

The production of hydroxyapatite prototypes from solid bodies of gypsum/polyvinyl alcohol composites

Prototypes of porous hydroxyapatite (HAp) were produced from Gypsum/PVA composite, using a mass proportion of 15% polymer. The material was obtained by means of chemical conversion in (NH4)2HPO4 0.5 mol.L-1 solution and NH4OH 6.0 mol.L-1 alkaline medium for pH control, maintained between 6.0 and 9.0. The reaction occurred at a temperature of 100oC at different test times. The obtained HAp was characterized by several techniques, such as FTIR, which identified the SO42- groups characteristic for the Gypsum block, and the PO43- groups that are attributed to the biomaterial HAp, besides XRD and SEM, which made it possible to confirm a successful conversion of the material. Tests for mechanical resistance to compression (σc) were carried out for both materials as well.

Production of Hydroxyapatite/Polyhydroxibutirate Based Composites for Biomaterials Applications

Hydroxyapatite (HA) is a ceramic material broadly studied due to its great similarity with the human bone. However, this material presents high stiffness and young modulus in comparison with the bone tissue. The polyhydroxybutyrate (PHB) is a themoplatic and biodegradable polymer that presents bone like young modulus and gradative degradation that results in a permanence of the mechanical properties after implantation. The aim of this study is to evaluate the effect of the infiltration of melted PHB on the mechanical properties of porose HA bodies. The composite samples were characterized by SEM, EDS and compressive strength. The samples produced with 10% paraffin and sintered at 1200 °C showed the best mechanical properties and reached an increase of the compressive strength from 29,00 ± 4,70 MPa before infiltration to 83,00 MPa ± 4,41 after infiltration with PHB for a final porosity of 5%.

Caracterização química, mecânica e morfológica do gesso obtido do pólo do Araripe

Gypsum is a calcium sulfate hemihydrate with chemical formula CaSO4.0.5H2O, largely produced in Araripe, state of Pernambuco, Brazil, and features a purity ranging from 80 to 95%; their implementation is mainly based on the construction and also in dentistry, chemical industry, orthopedics, etc.. Due to the high quality of raw material and the low use of gypsum materials and objects with higher added value, there was the need to characterize the raw material for a better knowledge of its properties. FTIR, XRD, XRF, SEM, compressive and flexural strength, evaluation of porosity, particle size analysis and evaluation of the setting time of the paste procedures were performed. This study aims to know in detail the chemical, morphological and mechanical characteristics of gypsum, to be able to improve its properties for application in new products.

Produção e estabilidade de conservação de farinha de acerola desidratada em diferentes temperaturas

O objetivo deste trabalho foi identificar a melhor temperatura de desidratacao para a producao de farinha de acerola de alta qualidade de consumo e estabilidade de parâmetros fisico-quimicos durante a conservacao. Frutos de acerola, Flor Branca, foram colhidos no estadio de maturacao maduro em um pomar comercial do Vale do Sao Francisco, Petrolina, PE. Frutos com ou sem sementes foram sanitizados e desidratados nas temperaturas de 60 °C, 70 °C e 80 °C em estufa de circulacao de ar forcado e, em seguida, foram triturados para a obtencao da farinha, a qual foi armazenada em temperatura ambiente em embalagens de polietileno hermeticas. A polpa dos frutos foi utilizada para a determinacao do pH, solidos soluveis (SS), acidez titulavel (AT), acido ascorbico (AA) e umidade. A farinha de acerola foi avaliada a cada 15 dias, por um periodo de 75 dias, quanto ao pH, SS, AT, AA e cor. Para todas as temperaturas de desidratacao, os valores de pH e SS foram semelhantes, variando entre 3,5-4,2 e 6,3-11,7, respectivamente. Os SS apresentaram menor variacao ao final do armazenamento. A AT aumentou em todas as amostras variando de 5% a 10%. As perdas de acido ascorbico foram de 76,2% e 80%, 23,9% e 55%, ou 37,9% e 65% para as farinhas com e sem sementes desidratadas a 60 °C, 70 °C e 80 °C, respectivamente. De acordo com os resultados obtidos, a melhor temperatura de desidratacao e 70 °C, pois resultou em farinha com alta qualidade de consumo e estabilidade de parâmetros fisico-quimicos durante 75 dias de conservacao.

Production of Single-Phase Hydroxyapatite Porous Bodies from Gypsum/Polystyrene

Porous bodies were produced using hydroxyapatite as a starting material, gypsum, high purity material, low cost and that can be molded into the desired shape. Also, beads of polystyrene polymer. The first step of this work was to produce porous gypsum blocks obtained by mixing gypsum, water and polystyrene. After drying, they were submerged in acetone solvent for solubilizing the polymer and pore formation. The porous hydroxyapatite was synthesized in a second stage, where the porous gypsum blocks were immersed in a solution of (NH4)2HPO4 0.5 mol L-1 to 100 ° C and pH 7.0-9.0 for 24 hours. From this method, it was possible to produce bodies single phase hydroxyapatite with a maximum porosity of 70 ± 3% and a compressive strength of 1.48 ± 0.17 MPa.

Modeling of Two-Dimensional Orthotropic Heat Conduction in Porous Gypsum

The gypsum is a versatile material that shows low thermal conductivity, which makes this material very suitable for application as thermal insulation. The increase of the porosity of gypsum bodies promotes a decrease on the thermal conductivity. This effect optimize the range of applications of gypsum on the thermal insulate field. The present study aimed the numerical modeling of two-dimensional heat conduction by finite differences in a steady state to evaluate the ortotrophy of the thermal conductivity of porous gypsum using the elements of the protected hot plate method. Computer simulations were performed using thermal conductivity of the gypsum equal to 0.35 W/m.K. This value was varied on the x and y directions by 5%, 10% and 15%. The heat flow applied to the numerical simulations were equal 75 W/m2, 100 W/m2 to 125 W/m2.It was possible to produce temperature profiles where is visible the displacement of isotherms as a function of the change in thermal conductivity in the x direction.