Ana Paula Santana Musse

Automated system to acquire fluorescence, polarization and anisotropy maps within liquid flows.

Maps of polarization and anisotropy can be helpful for flow analysis systems (FIA, CFA, etc.) with reactions dependent on the intermolecular alignment as well as for dispersion control. Maps can be acquired manually, but when a scan over a sample area is required, the acquisition becomes tiresome and has low precision. The paper describes an automatic flexible system for high-precision sample positioning with closed loop self control, remote data acquisition and storage controlled by a BASIC program. The system was developed to acquire maps up to 850 mm2 of the sample (liquid flows, solids, interfaces, etc.), with up to 100 μm2 precision. To evaluate the equipment, performance is presented as the scan of a thin liquid film of monoethylene glycol (MEG) flowing on borosilicate. Tests were performed with and without surfactantes at submicellar concentrations: two concentrations of sodium dodecyl sulphate (SDS) and one of polyethylene oxide (PEO). For pure MEG, the intermolecular alignment initially increased, then decreased. When SDS was added, both polarization and anisotropy only increased progressively with the flow. This might be explained by the surfactant decrease of interfacial interaction. When PEO was added, both polarization and anisotropy decreased pronouncedly over the entire map, which might be due to macromolecular aggregates within the bulk generating misaligned molecular domains. The system presented as sample positioning repeatability of 0.1% and a high polarization reproducibility (error margin < 6 in 1000).

Wettability under Imposed Flow as a Function of the Baking Temperatures of a DGEBA Epoxy Resin Used in the Crude Oil Industry

The baking temperature (Tb) of an epoxy resin was optimized in order to decrease the dynamic interfacial tension, identifying the lowest wettability conditions for liquids flowing at a high rate. The dependence of dynamic interfacial tension on Tb was evaluated for the diglycidyl ether of bisphenol A. This resin was used to coat a sucking rod at the oil field of Bacia de Sergipe/Alagoas, Brazil in order to reduce blockage occurrences, maintenance stops, and the pumping capacity required. The samples were baked for 24 h between 100 and 180 °C. Their color and absorption spectra showed progressive dependence of Tb, indicating a migration from polymerization, through polymer network degradation, until carbonization. Spectrofluorimetry showed an initial increase in the energy gap between absorption and emission followed by a decrease that was attributed to changes of the chemical environment isotropy. Fourier transform infrared spectroscopy showed that the maximum polymerization occurred at 140 °C. Dynamic in...