In field efficacy trials most glyphosate/surfactant combinations tested control barnyardgrass as well as preormulated glyphosate products 21 days after treatment (DAT). Preormulated glyphosate products controlled barnyardgrass quicker than combination treatments, most likely due to improved glyphosate formulations with improved surfactant systems. In greenhouse trials, preormulated glyphosate products exhibited greater fresh weight reductions across all species tested, including barnyardgrass, broadleaf signalgrass, hemp sesbania, johnsongrass, large crabgrass, pitted morningglory, prickly sida, sicklepod, yellow foxtail and Palmer amaranth. Nonionic tallow amine treatments exhibited variable control among species. A shikimate analysis was developed using non-glyphosate-tolerant soybean to estimate efficacy of surfactants; data were then correlated to the visual efficacy data on barnyardgrass in the field. However, there was not sufficient variability in barnyardgrass control to use the shikimate analysis as a predictor.

Numerical simulations utilizing the code SURFER++ with the incorporation of an insoluble surfactant in the VOF scheme were conducted to characterize the effects of surfactant on a drop in shear flow. The drop is suspended in a matrix liquid. A parameter called reduction, which specifically relates to a percentage decrease in effective surface tension, is used to measure the surfactant amount on the interface. In a model system where reduction = 0.1, viscosity ratio = 1 and density ratio = 1, it was found that stable drops tend to be more elongated and less inclined to the primary flow direction than drops unexposed to surfactant. This can be explained by the location of surfactant at the interface as the drop evolves. Breaking drops also show a flattened angle, but exhibit shorter necks and faster time to break than similar drops without surfactant. As reduction increases, various physical characteristics of the drops change across Reynolds number. / Ph. D.

In many experiments, surfactant adsorption and desorption at solid-liquid interfaces is found to be quite slow, considering that surfactants are small molecules. Attenuated total reflectance Fourier transform infrared spectroscopy was used to study the adsorption, desorption, and exchange of tetradecyltrimethylammonium bromide (C₁₄TABr) at the silicon oxide surface. The exchange of surfactant was monitored using protonated and perdeuterated C₁₄TABr. The data show that exchange of C₁₄TABr between the surface and the bulk solution is very fast, complete exchange occurs in less than 10 seconds. A simple exchange model suggests that the disassociation rate constant of a single monomer is no less than 1 s^-1, which is ~ 10⁴ times slower than monomer exchange in bulk solutions. The actual exchange rate may be greater than observed in the present work due to transport phenomena. The rates of exchange are similar at concentrations above and below the critical micellar concentration. Adsorption is similarly rapid, but under some circumstances there is a small residue of surfactant that is slow to desorb. Desorption experiments utilizing KBr solutions of high and low ionic strength show that two thirds of each adsorbed micelle is held by hydrophobic association, and the other third is electrostatically bound. Adsorption, desorption, and exchange experiments at temperatures of 11°C above and 8°C below the Krafft temperature (14.4°C) show similar kinetics. / Master of Science

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Chemical enhanced oil recovery (CEOR) has gained a rapid momentum in the recent past due to depleting reserves of “easy-oil” and soaring oil prices. Hence, CEOR is now being considered for several candidates with varied oils and reservoir conditions, which demands the need for large hydrophobe surfactants. A new class of thermally and chemically stable large hydrophobe surfactant, Guerbet alkoxy carboxylates (GAC) has been tested. Unlike Guerbet alkoxy sulfates, GAC are stable at all pH and can be extremely useful in cases where alkali usage is prohibitive. They also exhibit synergistic behavior with internal olefin sulfonates (IOS) and alkyl benzene sulfonates (ABS), with the mixture showing enhanced calcium tolerance than the individual surfactants. Furthermore, in an attempt to diversify the raw material base, a new class of hydrophobe, viz. tristyrylphenol (TSP) based on petrochemical feed stock has also been developed and evaluated. Given the fact that there are hundreds of surfactants that can be tested for a particular candidate, the difficulty often lies in choosing the right surfactant to begin with. In an attempt to simplify that, a new correlation to predict the optimum surfactant structure has been developed. It relates the optimum surfactant structure to the formulation variables like oil properties, salinity, and temperature, including the parameters like PO and EO for new-generation surfactants. The correlation can serve as a guideline in choosing the optimum surfactant and will help in improving our understanding of the relationship among variables affecting the optimum surfactant structure. Surfactant retention is an important factor affecting the economics of chemical flooding and has to be studied carefully. Using an extensive data obtained from core flood studies a new correlation for predicting surfactant retention including the variables like pH, TAN, salinity, mobility ratio, temperature, co-solvent, and surfactant molecular weight has been developed. All these are new and highly significant advance in the optimization of chemical EOR processes that will greatly reduce the time and cost of the effort required to develop a good formulation as well as to improve its performance. / text

No description available.

No description available.

No description available.

Neste trabalho estudou-se a formação de complexos entre polieletrólitos e surfatantes de cargas opostas e uma nova rota para sintetizar partículas poliméricas estáveis, na qual a polimerização ocorre dentro dos complexos. O comportamento de misturas formadas pelo poliânion carboximetilcelulose (CMC) e o surfatante catiônico brometo de cetiltrimetilamônio (CTAB) e pelo policátion quitosana (CH) e o surfatante aniônico dodecilsulfato de sódio (SDS) foi investigado na interface líquido-ar por medidas de tensão superficial e na solução através de medidas de turbidez e condutividade. Foi avaliado o efeito da massa molar viscosimétrica média e da densidade de carga dos polieletrólitos na formação dos complexos. A síntese de poliestireno e poli(metacrilato de metila) em emulsão foi realizada na concentração de agregação crítica (cac) do sistema CMC/CTAB. As partículas híbridas foram caracterizadas por medidas de potencial zeta, espalhamento de luz e microscopia eletrôncia de varredura. Todas as dispersões foram estáveis na força iônica de 2,0 mol L-1 de NaCl durante quatro dias. A estabilidade coloidal foi atribuída à presença de uma camada de hidratação formada pela CMC em volta das partículas. Esta nova rota sintética tem a vantagem de produzir partículas de látex estabilizadas com uma quantidade reduzida de surfatante. / This work reports the complex formation between polyelectrolytes and opposite charged surfactants, and a new procedure to synthesize stable polymeric particles, where the polymerization takes place inside the complex. The behavior of mixtures of carboxymethylcellulose (CMC) and the cationic surfactant cetyltrimethylammonium bromide (CTAB), and chitosan (CH) and the anionic surfactant sodium dodecilsulfate (SDS) was investigated in the diluted range at the liquid-air interface by means of surface tension, and in the bulk solution by turidity and conductivity measurements. The effect of the molecular weight and charge density of the polyelectrolytes on the complexation with oppositely charged surfactants was studied. The synthesis of polystyrene or poly(methyl methacrylate) was carried out by emulsion polymerization in the critical aggregation concentration (cac) of the CMC/CTAB system. The hybrid particles were characterized by zeta potential, and light scattering measurements, and scanning electron microscopy. All dispersions were stable in the ionic strength of 2.0 mol/L NaCl at least during four days. The colloidal stability was attributed to the presence of a hydrated CMC layer around the particles. The present procedure brings the advantage of synthesizing and stabilizing particles with funciotnal groups on the surface in a one-step method using very small amounts of surfactant, a friendly condition for the environment.

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