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The Development of new materials for building industry is a necessary issue to promote sustainability. Gypsum is an important low cost material very abundant in the northeast region of Brazil. Its physical properties make it an interesting material to form composite materials. This work presents a study of gypsum reinforced with Caroá (neoglasiovia variegate) natural fibers, where different amounts of fibers (1, 2, and 3%) were added into gypsum matrix. Three different fiber sizes (5, 10, and 20mm) were used to evaluate the effect of fiber size on the properties. PVAc was added in order to enhance the interactions between matrix and fibers. Mechanical strength was characterized by compression and bending tests. The addition of 1% mass Caroá fibers leads to a slightly increase on the mechanical strength independently of fiber size.

Calcium sulfate dehydrate β (CaSO4. 0,5H2O) is a material obtained from the calcination of gypsite (CaSO4.2H2O). This is a low cost ceramic material very used in building industry. The improvement of their applications is of fundamental technological interest. Polymers are an interesting alternative of reinforcement. Polyvinyl acetate (PVAc) is an addition polymer obtained by the polymerization of vinyl acetate. This polymer is well known to achieve good adhesion to cellulosic surfaces. The aim of this work was to evaluate the mechanical properties of porous plaster bodies reinforced with PVAc. Mechanical behavior was characterized by compression and bending strength. Three water / gypsum ratios: 0.5 0.6 and 0.7 were used on this work. An amount of 5% and 10% PVAc promoted increase on the mechanical properties of gypsum. Higher amounts polymer promoted further decrease of the mechanical properties.

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.

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.

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%.

β-Tricalcium phosphate (β-TCP) ceramics are of interest for bone requirements implants due to resoption behavior. The mechanical properties of β-TCP, however, are not yet sufficient to allow load bearing application of implants. The aim of this work was to investigate the effect of Mg2+substitution on the strength sintered TCP. Due to promotion of a liquid phase at 1200°C, Calcium pyrophosphate (CPP-C2P2O7) was used to improve the sintering of the samples. The introduction of CPP was promoted by use of a Ca/P molar ratio of 1.45. The powders were synthesized using a mixture of Ca (OH)2suspension and diluted H3PO4with addition of MgO and calcined at 750 °C, 900 °C and 1050 °C. The cold isostatic pressing compacts were sintered at 1200 °C and 1300 °C, respectively.It was shown that a small Mg content (1.5 mol%) increased both compressive strength and fractional density of the TCP material sintered at 1200 °C from 132 ± 39 MPa at 92.1 % of fractional density to 193 ± 29 MPa at 94.5 % of theoretical density. Higher amounts of Mg inhibited the grain growth provoking a increase of the boundary mobility activation energy. Abnormal grain growth (AGG) was observed after sintering at 1300°C, as result CPP - liquid phase formation. Increase of Mg content promoted AGG, due to inhibition of grain growth during normal grain growth resulting in a increase of the residual elastic energy of the system.

Tricalcium phosphate based ceramics (TCP) are bioresorbable and thereby considered to be promising bone replacement materials. The differences in crystal structure between {alpha} and {beta}-TCP phases gives rise for different dissolution rates in vitro and in vivo, which may alter the bioresorbable behavior of TCP ceramics. It is suggested that the addition of magnesium ions, which are also present in biological tissues, stabilizes {beta}-phase to higher temperatures and thus enables the sintering of {beta}-TCP at elevated temperatures compared to Mg free TCP. In this paper, Mg-substituted TCP, with the general formula (Ca{sub 1-x}Mg {sub x}){sub 3}(PO{sub 4}){sub 2} and 0.01 {

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 SO4(2-) groups characteristic for the Gypsum block, and the PO4(3-) 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.