RESUMO
Polymeric composites have been widely used as dental restorative materials. A fundamental knowledge and understanding of the behavior of these materials in the oral cavity is essential to improve their properties and performance. In this paper we computed the data set of water absorption through an experimental dental resin blend using specimen discs of different thicknesses to estimate the diffusion coefficient. The resins were produced using Bisphenol A glycol dimethacrylate, Bisphenol A ethoxylated dimethacrylate and Triethylene glycol dimethacrylate monomers. The water sorption test method was based on International Standard ISO 4049 "Dentistry-Polymer-based filling materials". Results show a diffusion coefficient around 6.38 x 10(-8) cm(2)/s, within a variance of 0.01%, which is in good agreement with the values reported in the literature and represents a very suitable value.
Assuntos
Resinas Sintéticas/química , Resinas Sintéticas/metabolismo , Água/metabolismo , Adsorção , Bis-Fenol A-Glicidil Metacrilato/química , Bis-Fenol A-Glicidil Metacrilato/metabolismo , Difusão , Armazenamento de Medicamentos , Teste de Materiais/métodos , Teste de Materiais/normas , Metacrilatos/química , Metacrilatos/metabolismo , Modelos Teóricos , Polietilenoglicóis/química , Polietilenoglicóis/metabolismo , Ácidos Polimetacrílicos/química , Ácidos Polimetacrílicos/metabolismo , Valores de Referência , Resinas Sintéticas/normas , Fatores de Tempo , Água/química , MolhabilidadeRESUMO
The spiral pump (SP) uses centrifugal and axial pumping principles simultaneously, through a conical shaped impeller with threads in its surface. Flow visualization studies were performed in critical areas of the SP. A closed circuit loop was filled with glycerin-water solution (40%). Amberlite particles (80 mesh) were illuminated by a planar helium-neon laser light (7 mW). The particle velocities were recorded with Kodak (TMAX-400) black and white film, and the flow behavior was studied with a micro video camera and color video printer. The flow visualization studies showed no turbulence or stagnant areas in the inlet and outlet ports of the SP. When using the impeller with one lead, at the top of the threads some recirculation appeared when the total pressure head increased. Two new impellers were made. One of them had the same conical shape with a thread having 2 leads. The second had a thread with 2 leads, but it also had a bigger cone angle. These modifications improved the pump hydrodynamic performance, decreasing the recirculation in pumping conditions that require pressures over 200 mm Hg.