Vanessa Nóbrega Medeiros

Polyamide 6 Nanocomposites with Inorganic Particles Modified with Three Quaternary Ammonium Salts

The purpose of this study was to obtain polyamide 6 nanocomposites with national organically modified clay with three quaternary ammonium salts. The obtained results confirm the intercalation of molecules of salt in the clay layers, and a good interaction with the polymer, showing the formation of intercalated and/or partially exfoliated structures. The nanocomposites showed similar thermal stability compared to pure polymer, and the mechanical properties presented interesting and promising results.

Desenvolvimento de nanocompósitos de poliamida6/polietileno/argila organofílica: o efeito do compatibilizante PE-g-MA no comportamento reológico da mistura

O objetivo deste trabalho foi avaliar o efeito do compatibilizante PE-g-MA (5 e 10%) no comportamento reologico de nanocompositos de poliamida6/polietileno/argila organofilica, onde a argila foi tratada com um sal quaternario de amonio (Cetremide). Em geral, observou-se que a presenca do compatibilizante aumentou o torque da mistura de PA6/PE e que a presenca da argila organofilica (2%) sem o compatibilizante nao pareceu alterar o comportamento do torque da mistura. Por outro lado, para o nanocomposito com 10% em peso de compatibilizante e com a argila organofilica, verificou-se um aumento significativo do torque em relacao as outras misturas, evidenciando maior interacao da argila organofilica com as matrizes polimericas, isto e, maior viscosidade do sistema, promovida provavelmente pela presenca do compatibilizante. Os resultados de difracao de raio X mostraram que os sistemas apresentaram estrutura intercalada e/ou esfoliada.

Mechanical and thermomechanical properties of polyamide 6/Brazilian organoclay nanocomposites

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.

Evaluation of the effect of clay in polyethersulfone membranes

Polymeric membranes were produced from nanocomposites of polyethersulfone and clay, in proportions of 3 and 5% by weight of clay, by phase inversion technique using N, N-dimethylformamide as solvent. From X-ray diffraction analysis, an exfoliated and/or partially exfoliated structure was observed. From scanning electron microscopy images, it was observed that the nanocomposites membranes showed a surface free of defects, however, it was found in a cross section, an anisotropic structure, where the skin is thick and the porous support presents macropores. From water permeation flux measurements, it was found that the presence of the clay increased the flow, especially to the membrane with 5% of montmorillonite.

Analysis of the Efficiency of Surface Treatment of Bentonite Clay for Application in Polymeric Membranes

The bentonite clay fillers are mostly used for the development of nanocomposites, due to having characteristics which provide to obtain in nanometric particles. The bentonite clay was treated with an ammonium quaternary salt to modify it to organophilic clay. The polymeric membranes and nanocomposites were prepared using the phase inversion technique. The bentonite and organophilic clays were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The membranes were characterized by XRD. The results of XRF, XRD and FTIR confirmed the presence of quaternary ammonium salt in the organoclay structure. The XRD diffraction patterns of nanocomposites membrane showed exfoliated and/or partially exfoliated structure. According to the obtained results, it could be seen that the treatment performed on the surface of the clay was quite promising and efficient to be added as nanofillers on polymeric membranes.

Evaluation of impact strength of polyamide 6/bentonite clay nanocomposites

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.

Development of Polymer Membranes Modified with a Porogenic Agent

Membrane is a barrier that separates two phases and limits wholly or partially carrying one or several chemical species present in the phases. In this study, membranes with a polyamide6 porogenic agent were obtained. The membranes were prepared as thin films by phase inversion method using the immersion technique, precipitation by varying the percentage of porogenic agent introduced and the time of exposure of the membranes during the process of immersion-precipitation. The membranes obtained were characterized by scanning electron microscopy (SEM). From the SEM photomicrographs, a large morphological change was observed over the entire surface layer of the membranes, significantly affecting the size and number of pores. Furthermore, porogenic agent promoted the formation of pores and the increase in planar microporous membranes obtained.

Influence of Content and Treatment of Clay in the Morphology of PES Membranes

Polymeric membranes were produced from the nanocomposites of polyethersulfone and clay (untreated-MMT and treatment-OMMT), by phase inversion technique, in the proportions of 3 and 5% w/w, using as the solvent N, N dimethylformamide (DMF). From XRD results it was noted a change in the structure of the MMT by organophilization process with increase of the interplanar basal distance. To the membranes it was observed an exfoliated and/or partially exfoliated structure. From SEM images the nanocomposite membranes showed a surface apparently exempt of pores, however in the cross-section images shows an anisotropic structure, where the skin is dense and the porous support displays macrovoids. By the flow measurement, it was found that the compositions presented the same tendency in the flow lines, where the flow is high on the beginning and drops over time; and the inclusion of clay increases the flow, especially to the membranes with MMT 5%.

Influence of Molecular Weight of Polyamide 6 in Obtaining of Nanocomposites with National Organoclay

Much attention is being given to developing nanocomposites with layered silicates, owing to the great need for advanced materials engineering and the fact that the pure polymers do not present the behavior or properties needed for certain applications within that context, the objective of this study was to influence of the molecular weight of polyamide 6 in obtaining nanocomposites with national organoclay. For this, the mixture of polyamide 6/ organoclay was processed in a twin screw extruder, and then was characterized by thermogravimetry (TG), X-ray diffraction (XRD) and heat deflection temperature (HDT). It was then possible to observe by XRD to obtain a structure exfoliated or partially exfoliated in the studied systems. For TG, it was found that the nanocomposites were stabilities higher than the pure polymer. And the values of HDT of systems were significantly higher than those of pure polyamide 6.

Influence of Additives on Hybrids Membranes Morphology for Water Treatment

In this work, polyamide 6 membranes (PA6) and hybrids with 1, 3 and 5% of montmorillonite clay (MMT) were obtained, adding potassium chloride (KCl) and calcium chloride (CaCl2). These different additives are intended to promote formation and increase of the pores in the microporous membranes. The membranes in the form of thin films were prepared by the phase inversion technique, leading to flat selective barriers. The MMT clay was characterized by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). The membranes were characterized by XRD, FTIR, scanning electron microscopy (SEM), contact angle, water vapor permeation, flow measurements and yield. The clay XRD results showed characteristic peaks of bentonite containing accessory materials, as well as a peak at 5.93°, indicating the d001 basal interplanar distance of 14.95 Å of MMT. In the spectrum in the infrared region of the clay, it was observed the presence of hydroxyls inherent to the adsorbed water, as well as characteristic bands of Si-O-Si bonds and the octahedral layer of MMT. The viscosities of the solutions of PA6 and their hybrids with CaCl2 were higher compared to solutions containing KCl due the CaCl2 possess a bivalent ion with a high degree of hydration and a molecular mass higher than KCl. In addition, these salts promote formation of hydroxides that precipitate the particles of MMT, decreasing the viscosities with the increasing percentage of clay. By means of the X-ray diffraction, it was possible to perceive that the hybrid membranes with the inorganic salts suggest an exfoliated and/or partially exfoliated structure. From the results of the FTIR analysis the bands obtained in the PA6 membranes and its hybrids remained practically unchanged, as there was an increase in the clay content and the introduction of the inorganic salts. From the photomicrographs obtained by SEM, it was observed that the addition of clay in the hybrid membranes provided an increase in the number of pores with the gradual increase of the percentage of clay. While the addition of the inorganic salts (KCl and CaCl2) provided an increase in the pore size of the top surfaces of all membranes, by means of the contact angle, it was verified that the hybrid membranes presented smaller angles when compared to the PA6, probably, due to the superficial peculiarity of the clay to react with water. PA6 membranes with KCl and CaCl2 showed lower water vapor permeations as compared to hybrid membranes due to the increase in the size and quantity of pores presented on their top surfaces. The distilled water flow in the membranes initially showed a decrease and after 30 minutes a stability of the permeate flow due to a compression occurred in the membranes. The water-oil separation tests of the membranes with CaCl2, regardless of the pressure used, indicated a significant reduction of permeate oil with promising yields above 87% , presenting potential for the treatment of wastewater contaminated by oil.