RESUMO
The influence of ammonium polyphosphate (APP) particle size on the performance of an intumescent formulation and on the synergistic action of a series of montmorillonite samples with different d-spacings for the production of flame retardant composites was investigated. The polymer matrix employed was poly(ethylene-co-butyl acrylate), EBA 30, and the intumescent formulation consisted of APP and pentaerythritol (PER). After being processed, the composites were submitted to scanning electron microscopy (SEM), thermogravimetric analysis, heating microscopy, and limiting oxygen index tests. The results indicate that the greater interaction between the APP and PER molecules, caused by the increase of the contact area promoted by the reduction of the APP particle size, could favor the esterification reaction between APP423 and PER, allowing the formation of a greater amount of char precursors in shorter period of time. In addition, the montmorillonite d-spacings had a more pronounced influence on the clays synergistic action with the intumescent formulation containing the APP with smaller particle size. Microscopy has shown to be an important tool to investigate APP particle size effect on the fire retardancy. AFM results enabled the detection of nanometric particles in the sample containing the smallest particle size of APP. SEM micrographs showed that those nanometric particles were better dispersed in the matrix, interacting more effectively with the other components, a factor probably responsible for the superior fire retardancy results. Heating microscopy revealed that the material with smaller APP particle size did show some remaining structure at the temperature of 850°C.
RESUMO
The aim of this study is the evaluation of partially sulfonated polystyrene nanoparticles (SPSNP) efficiency as nanocarriers for a non-ionic surfactant, oleic acid diethanolamide (OADA), in the reduction of the surfactant losses and the increase of oil recovery. The synthesized oleic acid diethanolamide was characterized by FTIR, 1H NMR, 13C NMR, surface tension (γ = 36.6 mN·m-1, CMC = 3.13 × 10-4 M) and interfacial tension of mineral oil/OADA aqueous solutions (IFTeq = 0.07 mN·m-1). The nanoparticles (SPSNP) were obtained by emulsion polymerization of styrene, DVB and sodium 4-styrenesulfonate (St-S) in the presence of OADA aqueous solution and were characterized by FTIR and PCS. The results show that the presence of ionic groups in the polymer structure promoted a better nanoparticles suspensions' stability, smaller particles production and more pronounced IFT reduction. The SPSNP obtained with an OADA concentration twenty times its CMC and 0.012 mol % of St-S presented a particle size around 66 nm and can act as efficient nanocarriers decreasing the water/oil interfacial tension to low values (0.07 mN·m-1) along the time, when in contact with the oil. Transport and oil recovery tests of the nanocarriers systems in an unconsolidated sand porous medium test show that the SPSNP do inhibit surfactant adsorption onto sand particles surface and induced an increase of oil recovery of up to about 13% relative to the water flooding oil recovery, probably due to a synergistic effect between the nanoparticles and surfactant action at the water/oil interface.