Influencia de alginato e quitosana na precipitação de fosfatos de calcio

Influence of alginate and chitosan on the precipitation of calcium phosphates

dc.creatorLima, Daniel Oliveira de
dc.date2006
dc.date2006-04-27T00:00:00Z
dc.date2017-03-29T11:18:28Z
dc.date2017-06-20T18:12:42Z
dc.date2017-03-29T11:18:28Z
dc.date2017-06-20T18:12:42Z
dc.date.accessioned2018-03-29T02:51:24Z
dc.date.available2018-03-29T02:51:24Z
dc.identifierLIMA, Daniel Oliveira de. Influencia de alginato e quitosana na precipitação de fosfatos de calcio. 2006. 113 p. Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica, Campinas, SP. Disponível em: <http://libdigi.unicamp.br/document/?code=000396398>. Acesso em: 29 mar. 2017.
dc.identifierhttp://repositorio.unicamp.br/jspui/handle/REPOSIP/266944
dc.identifier.urihttp://repositorioslatinoamericanos.uchile.cl/handle/2250/1322399
dc.descriptionOrientador: Marisa Masumi Beppu
dc.descriptionDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
dc.descriptionResumo: Não informado
dc.descriptionAbstract: Natural systems are able to create organic-inorganic composites of remarkable properties. Bone, for instance, presents properties that are found both in ceramics and polymers. This effect is related to the organic matrix, which controls nucleation and growth of calcium phosphate crystals, besides composite's organization and architecture in nanometric levels, in order to achieve a better understanding of this process, precipitation of calcium phosphate was carried out in a medium which contained small amounts of alginate and chitosan, seeking to emulate the matrix effect. Calcium phosphates precipitates were obtained using two different concentrations of the biopolymer and one control sample. The experiments were divided in two groups, depending on the system's initial pH. In the first group, the starting pH was acid. However, part of the reaction medium was separated and had its pH adjusted to an alkaline range. In the second group, the initial pH was calculated in order to be in the range of hydroxyapatite stability. Characterization was accomplished by scanning electron microscopy, X-Ray diffraction and Fourier-transform infrared spectroscopy. The powders obtained in the first group were compose mainly by brushite (CaHPO4.2H2O) and its anhydrous phase, monetite, CaHP04. In the first group of experiments with alginate, monetite concentration was related mainly to the reaction medium pH, suggesting that alginate-calcium interaction was strongly dependent on the formation of complexes among carboxyl radicals and calcium, which avoided water bonding. Chitosan-doped samples, on the other hand, seemed to be affected mainly by the biopolymer concentration. Chitosan and monetite concentration seemed to be inversely proportional. This is attributed to the ionotropic effect, which reduced auto-diffusion and consequently, calcium phosphate-chitosan interaction. These samples also possessed an apparent degree of orientation, supposedly due to a coherent growth of calcium phosphate crystals over heterogeneous nuclei. Alginate-doped samples obtained in the second group of experiments presented reduced cristal Unity, which was related to reprecipitation of the crystals over biopolymers nuclei. Chitosan-doped samples, however, presented an increase in crista!Iinity. This may be attributed to a process of nucleation inside the gel, implying in crystalline growth controlled by sterical effects
dc.descriptionMestrado
dc.descriptionEngenharia de Processos
dc.descriptionMestre em Engenharia Química
dc.format113 p. : il.
dc.formatapplication/pdf
dc.languagePortuguês
dc.publisher[s.n.]
dc.subjectQuitosana
dc.subjectAlginatos
dc.subjectFosfato de cálcio
dc.subjectChitosan
dc.subjectAlginate
dc.subjectCalcium Phosphates
dc.titleInfluencia de alginato e quitosana na precipitação de fosfatos de calcio
dc.titleInfluence of alginate and chitosan on the precipitation of calcium phosphates
dc.typeTesis


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