Study of mass transfer in oil–water–oil multiple emulsions by differential scanning calorimetry

Desenvolvimento de surfatantes para aplicação na indústria de explosivos

A comercialização dos explosivos emulsionáveis, aí incluída a dinamite de ANFO, acarretou um aumento significativo no consumo mundial de explosivos entre 1960 e 1980, conseqüência da maior segurança no transporte e no preparo dos explosivos na forma de uma emulsão. Os surfatantes utilizados nestas emulsões são ésteres, amidas ou imidas derivadas do poliisobutileno com terminações de anidrido succínico (PIBSA). Neste trabalho, surfatantes derivados da reação do PIBSA com polioxietilenodiaminas foram sintetizados e caracterizados pelas técnicas de espectrometria no infravermelho e de cromatografia de exclusão de tamanho. Os surfatantes sintetizados foram avaliados quanto ao efeito das suas estruturas na redução da tensão interfacial do sistema água em óleo e todos foram capazes de reduzir a tensão interfacial deste sistema.

Separating oil-water nanoemulsions using flux-enhanced hierarchical membranes

Membranes that separate oil-water mixtures based on contrasting wetting properties have recently received significant attention. Separation of nanoemulsions, i.e. oil-water mixtures containing sub-micron droplets, still remains a key challenge. Tradeoffs between geometric constraints, high breakthrough pressure for selectivity, high flux, and mechanical durability make it challenging to design effective membranes. In this paper, we fabricate a hierarchical membrane by the phase inversion process that consists of a nanoporous separation skin layer supported by an integrated microporous layer. We demonstrate the separation of water-in-oil emulsions well below 1 μm in size. In addition, we tune the parameters of the hierarchical membrane fabrication to control the skin layer thickness and increase the total flux by a factor of four. These simple yet robust hierarchical membranes with engineered wetting characteristics show promise for large-scale, efficient separation systems.

Assessment of Physical Stability and Antioxidant Activity of Polysiloxane Polyalkyl Polyether Copolymer-Based Creams

The purpose of the present work was to investigate the changes on physical stability (color, creaming, liquefaction, pH, conductivity, centrifugation, viscosity and rheological parameters) by non-ionic surfactant polysiloxane polyalkyl polyether copolymer based creams following inclusion of plant extract containing phenolic compounds. The antioxidant activity of the plant extract alone and after addition in the cream was assessed using the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. Physical stability was assessed by submitting the creams to storage at 8°C, 25°C, 40°C, and at 40°C with 70% RH (relative humidity) for a period of two months. Physical characteristics of polysiloxane polyalkyl polyether copolymer based creams, that is, color, creaming, liquefaction, centrifugation and pH were noted at various intervals for 2 months. The viscosities and rheological behavior of creams were determined using a rotational rheometer. Data were analyzed by using Brookfield Software Rheocalc version (2.6) with IPC Paste and Power Law (PL) math models. Cream with plant extract showed pseudo plastic behaviour with decreasing on viscosity. TheAcacia nilotica(AN) extract alone and the cream containing this extract showed great antioxidant and free radical scavenging activities. Power Law and IPC analysis were found to fit all the rheograms.

Critical review of techniques and methodologies for characterization of emulsion stability

The efficient development and production of high quality emulsion-based products depends on knowledge of their physicochemical properties and stability. A wide variety of different analytical techniques and methodologies have been developed to characterize the properties of food emulsions. The purpose of this review article is to provide a critical overview of the most important properties of emulsions that are of interest to the food industry, the type of analytical techniques that are available to measure these properties, and the experimental protocols that have been developed to characterize the stability of food emulsions. Recommendations are made about the most suitable analytical techniques and experimental protocols needed to characterize the stability and properties of food emulsions.

Modelization of the release from a tetradecane/water/hexadecane multiple emulsion: evidence of significant micellar diffusion

The release of tetradecane from a multiple emulsion of the type tetradecane/water/hexadecane was studied experimentally using the differential scanning calorimetry technique. The kinetics of the tetradecane release was measured for three formulations containing different concentrations of hydrophilic surfactant (2%, 4%, and 7%). A new mass transfer model derived from the shrinking core model was developed. The values of the model parameters deduced from the least-squares fittings led to the determination of the tetradecane diffusivity. Thus, the preponderant mechanism of mass transfer was proved to be micellar diffusion and not molecular diffusion. This conclusion was confirmed by considering the effect of the change in the hydrophilic surfactant concentration.

Morphology characterization of emulsions by differential scanning calorimetry

This article is a review of some results obtained by Differential Scanning Calorimetry (DSC) for characterizing the morphology of emulsions. In a classical DSC experiment, an emulsion sample is submitted to a regular cooling and heating cycle between temperatures that include freezing and melting of the dispersed droplets. By using the thermograms found in the literature for various emulsions, how to get information about the solidification and melting, the presence of solute, the emulsion type, the transfer of matter, the stability and the droplet size is shown.