Papers by Author: Sara Verusca de Oliveira

Abstract: Polyethylene (PE) nanocomposites were prepared by melt intercalation, in order to evaluate the flame retardant effect of this material. For the development of nanocomposites were used the montmorillonite clay (MMT), organoclay (OMMT) and flame retardant product (FRP) with the percentage of 1, 3, 6 and 9 wt%. Grafted polyethylene with maleic anhydride (PE-g-MA) was used as a compatibilizer of the systems. PE and its systems were evaluated: XRD, TEM, TG and flammability (UL94HB, oxygen index (LOI) and cone calorimetry). The X-ray diffraction showed a partial intercalation and exfoliation as well as formation of microcomposite. The phase morphology of the systems was observed by TEM that it showed that the system with 1% OMMT clay presented a predominance of exfoliation. Already the system with 3% OMMT showed partial exfoliation and this exfoliation reduced as the clay content increased. By TG it was seen that MMT, OMMT and FRP acted improving the thermal behavior of the nanocomposites compared to PE matrix. The results obtained for the oxygen index showed that both PE and its systems presented flame retardancy behavior. By means of the horizontal flammability tests, it was found that the presence of 1% MMT clay reduced 25% the flammability of PE. By cone calorimetry it was found that the system that contains 9% of OMMT clay decreased by about 33% the flammability of PE.

Abstract: The development of nanocomposites polymer matrix with clay from Brazil has been naturally abundant and low cost alternative. In this study, we obtained nanocomposites polyamide66 (PA66) with 1% and 5% of bentonite clay from Brazil, to be used as microporous organic/inorganic hybrid membranes. The clay was treated with a quaternary ammonium salt in order to make it organophilic. The membranes in the form of thin films were prepared using the technique of immersion-precipitation of solution from the nanocomposites. Treated clay and untreated clay were characterized by X-ray diffraction (XRD) and Thermogravimetry (TG). The membranes were characterized by TG and XRD. The result of XRD showed the presence of quaternary ammonium salt in the structure of clay, after organophilization. For TG, we observed that the treated clay showed higher thermal stability when compared to untreated clay. For TG, we observed that in general the membranes of PA66 with treated clay, present decomposition temperature higher when compared with untreated clay, thus revealing a greater thermal stability of membranes PA66 with treated clay. Through the X-rays patterns, it was found that membranes with 1% of nanoclay present exfoliated structure and can therefore be applied as microporous membranes.

Abstract: Nanocomposites are hybrid materials that can be obtained with, three, two or bust one-dimensional in nanoscale found in particles dispersed in the matrix. By presenting a nanometric structure, this new class of materials may have only properties, different from traditional composites and their constituents, which may be established in the synthesis process. The aim of this work is prepare nanocomposites of HDPE/ bentonite clay by melt intercalation technique. Systems were evaluated for the presence of untreated clay and chemically treated (organoclay) with two different types of quaternary ammonium salts, Cetremide and Dodigen. In the preparation of nanocomposites were obtained concentrated using a high speed mixer and then the nominal percentage of clay was dispersed in a twin screw extruder corrotacional. The systems were characterized by X-ray diffraction and mechanical properties. The XRD patterns of nanocomposite of HDPE/organoclay suggest a not intercalated structure. The mechanical properties of nanocomposites presented reducing values in relation to pure polymer.

Abstract: This research is to obtain nanocomposites of HDPE/bentonite clay. Inorganic polymers reinforced with materials are of great interest due to their applications in automotive, and electrical and electronic industries. The nanocomposites were produced by melt intercalation with different percentages of clay and compared with pure HDPE. Clay was used as modified and unmodified and it was characterized by X-ray diffraction (XRD) and X-ray fluorescence (XRF). The obtained nanocomposites were characterized through thermogravimetry (TG). It was verified by XRF that clay performed compositions of bentonites characteristics. By XRD, it was observed increases basal spacing for organoclay. By TG, in general, it was verified that the nanocomposites presented greater thermal stability in relation to HDPE.

Abstract: This research was incorporated the hydroxyapatite in a mineral trioxide aggregate sealer, with the aim of studying this influence in the structure, morphology and radiopacity of the cement to obtain osteoconductive material. The samples were characterized by X ray diffraction (XRD), spectrometry fluorescence X ray (EDX), spectroscopy transform infrared Fourier (FTIR), scanning electron microscopy (SEM) and radiographic appearance. Through the results obtained by XRD for the new sealer observed the formation of phases HAp and MTA evidenced by the presence of phases: CaO, SiO₂ and Bi₂O verified also by EDX. Through FTIR was observed the presence of absorption bands related to links Ca-O, Si-O and Bi-O present in MTA and P-O present in HAp. The morphology visualized by SEM consists of irregular agglomerates with the formation of pre-sintered particles. The sample MTA/HAp3% presented radiopacity viable for their application as endodontic cement.

Abstract: The search for new sources of renewable energy order to minimize environmental impacts has led the scientists to develop new alternatives, such as the use of recycling of frying oils to produce biodiesel. The utilization of fuels of agricultural origin in the cycle diesel engines is a good alternative to reduce dependence on importation petroleum, since these fuels are a renewable source of energy. The utilization of biodiesel as biofuel is a contribution to the environment, reducing the qualitative and quantitative form levels of environmental pollution. However, these oils should go through a process of decontamination and decoloration up the stage of chemical conversion which is used clay to lighten the oil. This study aimed to characterize clay of Paraíba to be used in the clearing of frying oil. It was observed through the technique of kinematic viscosity the clays show good results in treatment used vegetable oils.

Abstract: The development of research in the area of advanced materials and tissue engineering has increased greatly in recent years found that bioceramics are outstanding in the replacement and regeneration of bone tissue, mainly formed by the calcium phosphate ceramics. The objective of this research is to obtain the calcium phosphate where Ca/P = 1.67 and 2.0, to observe the formation of phases after having subjected these materials to heat treatment. The calcium phosphate was produced by the wet method using a direct reaction of neutralization and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray microanalysis (EDS). The XRD results confirm the presence of hydroxyapatite phase in the sample with Ca/P = 1.67, where as the phosphates prepared with Ca/P = 2.0 ratio show a combination of hydroxyapatite and phase β- tricalcium phosphate. The micrographs obtained are characteristic of ceramic material called calcium phosphate. EDS confirmed the presence of Ca, P and O in the material.

Abstract: In bioscience, there are several apatites constituteds by differents compositions. In the biological environment, apatites are found in bones and teeth of vertebrates with Ca/P ration from 2.0 to 0.5. It is not easy to determine the exact proportion of Ca2 + and PO43- in solution in the preparation of the process. In this study, apatites with Ca/P ration 1.0, 1.67 and 2.0 were prepared by direct reaction in an solution of H3PO4 in a suspension of Ca(OH)2, of same molarity, evalueting the crystallinity of CPP, Hap e TeCP with 1 mol/l, 3 mol/l and 5 mol/l. The samples characterized by X-ray diffraction (XRD) were compared with the standard of reference of the data base JCPDS. The composition of calcium phosphate for the differents molarity studied, resulted in a combination of phases with the exception of hydroxyapatite Ca/P ration 1.67 at concentrations 1 mol/l and 3 mol/l. But the diffractograms revealed that the increased molarity provided a decrease of some peaks of reflection of calcium phosphates with Ca/P ration 1.67. However, for the Ca/P ration 1.0 increasing the concentration, showed an increase of crystallinity of calcium phosphates. The FTIR confirmed the presence of phosphates in the spectrums around 1045 cm-1. The calcium phosphates obtained through direct reaction showed Ca/P ration is related with the technique employed, consolidating it in the preparation of these bioceramics.

Abstract: Calcium carbonate (CaCO3) is a ceramic of strong economic potential, given the versatility of its application in industry in many different areas. Protective shells of marine snails of the Brazilian coast were analyzed in this study, to verify the content of calcium carbonate available in this type of material. The samples were collected at Bessa´s Beach located in the João Pessoa’ coast Capital of Paraíba state, northern Brazil. The collection occurred during the month of February 2008; the sample was processed into powder and it was examined by X-ray Fluorescence (XRF), X-ray diffraction (XRD) and Infrared Spectroscopy with Fourier Trasformating (FTIR). The material was also submitted to heat treatment at 110°C and characterized by same techniques. The results confirmed the presence of a high content of calcium carbonate in the samples (over 95%,) which has not changed with the heat treatment used. It was presents the morphologies calcite and aragonite with prevalence of the second, both showing high levels of crystallinity. From the results obtained, calcium carbonate of the coast Paraíba has a potential application like bioceramic.