The aim of this work was to prepare hollow fiber membrane changing the composition of polyethersulfone, polyvinylpyrrolidone (PVP) and clay, through the phase inversion technique, evaluating the influence of these constituents on the viscosity and distinct morphologies. Flat membranes were produced and their contact angles were determined and showed difference when clay was added and/or PVP. For the hollow fiber membranes, the +addition of these constituents, PVP and/or clay in the solution, can change significantly the viscosity and effect the membrane formation. From the scanning electron microscopy (SEM) images, it was identified the influence on morphology with the compositional variation of each additive, with the PVP promoting shorter precipitation time, favoring the formation of pores of the “fingers” type and increasing the presence of macrovoids. The addition of clay favored the formation of spherical pores, reducing the presence of macropores.

RESUMO Membranas podem ser consideradas películas poliméricas ou inorgânicas que funcionam como uma barreira semipermeável para uma filtração em escala molecular, separando duas fases e restringindo, total ou parcialmente, o transporte de uma ou várias espécies químicas (solutos) presentes na solução. Portanto, o objetivo deste trabalho é produzir membranas de poliétersulfona (PES) e poliétersulfona / argila pela técnica de inversão de fase e avaliar a presença de argila na obtenção de membranas para o tratamento de efluentes líquidos. O solvente utilizado foi a dimetilformamida (DMF) e argilas utilizadas foram Brasgel PA (MMT) e Cloisite Na (CL Na) nas proporções de 3 a 5% (em peso). Por difração de raios-X (DRX), as membranas com 3% das argilas MMT e CL Na aparentemente apresentaram estruturas parcialmente esfoliadas; para a composição com 5% de CL Na observou-se um pequeno pico, que indica que esta é, possivelmente, uma estrutura intercalada ou microcompósito. A partir dos resultados de microscopia eletrônica de varredura (MEV), visualizou-se que a superfície da membrana de PES puro apresentou uma estrutura aparentemente sem poros, no aumento utilizado e, uma superfície sem rugosidade quando comparada com às membranas com argila. As medidas de ângulo de contato indicaram que a inclusão da argila alterou a capacidade de molhamento das membranas. O fluxo com água destilada para todas as membranas iniciou alto e ao longo do tempo chegou a um patamar de estabilização. Assim, pôde-se concluir que a presença e o teor de argila alteraram a morfologia da membrana, contribuindo para um aumento do fluxo de água.

ABSTRACT Membranes can be considered polymeric or inorganic films that function as a semipermeable barrier to filtration on a molecular scale, separating two phases and restricting, totally or partially, the transportation of one or more chemical species (solute) present in the solution. Therefore, the aim of this work is to produce polyethersulfone membranes (PES) and polyethersulfone/clay by phase inversion technique and evaluate the presence of clay in obtaining membranes for wastewater treatment. The used solvent was dimethylformamide (DMF) and clays were Brasgel PA (MMT) and Cloisite Na (CL Na) in the proportion of 3 to 5% (wt.). By X-ray diffraction (XRD), the membranes with 3% of MMT and CL Na clays apparently had partially exfoliated structures. For the composition with 5% of CL Na a small peak was observed, which indicates that this is possibly an intercalated structure or microcomposite. By scanning electron microscopy (SEM), visualizes that the pure suface of the pure PES membrane a structure apparently without pores was observed in the used magnification and without roughness surface when compared to membranes with clay. The measurements of contact angle indicated that the inclusion of clay altered the wetting ability of the membranes. The flow with distilled water for all membranes started high and over time reached a stabilization level. Thus, it can be concluded that the presence and the content of clay altered the morphology of the membrane, contributing to an increase in water flow.

Abstract Polymer/clay nanocomposites are a new class of composites with polymer matrices where the disperse phase is a silicate with elementary particles that have at least one of dimensions in nanometer order. Polyamide 6/Brazilian organoclay nanocomposites were prepared by melt intercalation, and the mechanical, thermal and thermomechanical properties were studied. The structure and morphology of the nanocomposites were evaluated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was verified by XRD and TEM analysis that all systems presented exfoliated structure predominantly. By thermogravimetry (TG), nanocomposites showed higher stabilities in relation to pure polymer. It was observed that the nanocomposites showed better mechanical properties compared to the properties of polyamide 6. The heat deflection temperature (HDT) values of the nanocomposites showed a significant increase in relation to pure polymer.

Membranas de híbridos orgânico/inorgânico de poliamida 6 e argilomineral constituído de silicatos em camadas foram estudadas em comparação com o polímero puro. Uma argila sódica, como recebida da indústria, e outra organofilizada com os sais quaternários de amônio Dodigen e Cetremide foram utilizadas. Os sais tornam hidrofóbica a superfície da argila e favorecem sua incorporação na matriz polimérica no estado fundido. A partir dos nanocompósitos obtidos foram preparadas membranas por meio da técnica de imersão-precipitação, tendo como solvente o ácido fórmico e como método de produção a precipitação em um banho de água (não-solvente). O teor do ácido nas soluções poliméricas, dos híbridos e da poliamida 6 pura, foi variado para avaliar sua influência na morfologia e na permeabilidade das membranas produzidas. As membranas apresentaram morfologia assimétrica, constituída de uma pele filtrante e um suporte poroso. A presença da argila tratada com os diferentes sais alterou a formação dos poros, tanto na superfície como na seção transversal. As partículas de argila provavelmente atuaram como barreira ao fluxo. Observou-se ainda que o teor de ácido utilizado influenciou de forma significativa a estrutura assimétrica da membrana; quanto maior o teor de ácido maior a espessura da pele filtrante. O teor de ácido também levou à alteração do tamanho e da distribuição dos poros. As medidas de fluxo realizadas com os dois teores de ácido diferentes mostraram uma resposta em função da morfologia diferenciada obtida.

Organic/inorganic hybrid membranes of polyamide 6 and mineral clay containing layers of silicate were prepared and compared to those of the pure polymer. Use was made of an as-received sodium clay from industry and another organophilized with ammonium quaternary salts (Dodigen and Cetremide). The salts make the clays surface hydrophobic and improve their incorporation into the polymer matrix in the molten state. Membranes were prepared with these nanocomposites using the immersion-precipitation technique with formic acid as a solvent, and precipitation in a water bath as non-solvent. The acid concentration in the solution containing the polymer and the hybrids was varied to study its influence in morphology and permeability of the membranes. An asymmetric morphology consisting of a filter skin and a porous support was observed, with pores both on the surface and in the cross section being affected by the different salts. This asymmetric morphology was also affected significantly by the acid concentration, with thicker filter skins for higher concentrations. The acid concentration affected the pores size and their distribution. The clay particles probably acted as a barrier to the flow. The permeating flux for the two acid concentrations varied as a function of the distinct morphologies.

Nanocomposites of polymer/clay have had much attention in recent years, particularly those developed with layered silicates due to the need of engineering materials more efficient than pure polymers for certain applications. The level of exfoliation of layered silicates in crystalline structure of polymer matrices has been studied and has been observed that it affects the crystalline behavior and the physical and mechanical properties. In this study, nanocomposites of polyamide 6 were obtained by the melt intercalation method, using a Brazilian bentonite modified with a quaternary ammonium salt. X-Ray Diffraction (XRD) results showed the incorporation of salt among the layers of clay, making it organophilic and that the nanocomposites presented exfoliated and/or partially exfoliated structures and confirmed by transmission electron microscopy (TEM). By thermogravimetry (TG), the results indicated that the presence of clay increased the thermal stability of polyamide 6. The impact properties of the nanocomposites showed inferior values in relation to the pure polyamide, in other words, decrease the toughness.