Papers by Author: Keila Machado Medeiros

Abstract: 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.

Abstract: The membrane separation processes have low power consumption, higher separation efficiency, simplicity of operation and high quality end product. In this work, hybrid membranes of polyamide6 with bentonite clay were obtained by adding an inorganic salt. The hybrids were obtained by the melt intercalation method. The membranes were prepared by phase inversion technique by varying the percentage of inorganic salt and the time of exposure of the membranes during the immersion-precipitation process. The hybrid and hybrid membranes with and without the addition of the inorganic salt were characterized by X-ray diffraction (XRD). The results from XRD showed that the hybrid and hybrid membranes with and without inorganic salt presented an exfoliated and/or partially exfoliated structure. The addition of the inorganic salt did not cause significant changes with respect to the crystalline behavior of the polymer under study.

Abstract: In this work, were obtained nanocomposite membranes polyamide66/Paraíba bentonite clay, treated with a quaternary ammonium salt in order to make it organophilic. The membranes were prepared as thin films using the technique of phase inversion from the nanocomposites obtained by solution. The membranes were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry (TG) and scanning electron microscopy (SEM). By means of X-ray diffractogram, it was revealed that the membranes remained organically treated clay presented exfoliated and/or partially exfoliated structure. From curves of DSC and TG, it was observed that membrane of PA66 with 3% w/w of with treatment clay showed higher thermal stability compared with the same content of clay without treatment. From the SEM photomicrographs, there was a selective layer (skin filter) on top and one porous layer at the bottom of all membranes studied. Moreover, it was verified that the presence of clay provided a significant structural modification in the membranes of polymer nanocomposites.

Abstract: 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.

Abstract: Recent advances in biodegradable polymers have attracted a great interest not only in traditional areas such as biomedical and pharmaceutical industry, but also in packaging applications, articles and injected membranes. The aim of this work was to produce bio-nanocomposites poly (lactic acid) - PLA with bentonite clay. The bio-nanocomposites were produced by melt intercalation with incorporation of 1 to 3 wt% of organoclay. The degree of dispersion of clays in the polymer, and consequently the structure of bio-nanocomposites produced was evaluated by X-ray diffraction (XRD), and the thermal properties were studied by differential scanning calorimetry (DSC). XRD results indicated the formation of intercalated structures. It was observed the appearance of crystalline melting double peaks in bio-nanocomposites PLA.

Abstract: The nanocomposites are hybrid materials where at least one of the components has nanometric dimensions and in the same way as traditional composites are formed, one of the components is the matrix in which nanoparticles are dispersed. One of the possibilities of applications of nanocomposites is to obtain polymer films for applications in the barrier, or separation promoted by the dispersion of the clay lamellae. In this work, nanocomposites of nylon 6/bentonite clay were obtained by melt intercalation. The used clay was the Brasgel PA, and quaternary ammonium salt was Praepagen-HY, used in organophilization of the clay. By XRD, it was observed the disappearance of the characteristic peak of clay, and this can be facilitate the possible exfoliation of clay in the produced films from the nanocomposite. By SEM, it was observed, an apparently dense layer with no pores.

Abstract: Membranes can be defined as polymer film that acts as a semipermeable barrier to filtration in a molecular scale, separating two phases. In this work, microporous membranes were obtained from hybrid organic/inorganic polyamide66 (PA66) and clay mineral from Paraíba State, treated with a quaternary ammonium salt in order to make it organophilic. The membranes in the form of thin films were prepared by immersion-precipitation technique from the nanocomposites obtained by solution, with a pre-determined reaction time of 2 h, with characteristics suitable to be used in microfiltration process for separation of the oil present in water. Samples of natural and organophilic clay were characterized by X-ray fluorescence (XRF) and Fourier transform infrared spectroscopy (FTIR). Meanwhile, the membranes were characterized by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results of FRX and FTIR confirmed the presence of quaternary ammonium salt in the clay structure after treatment with organic salt. Through DSC analysis it was observed almost no change in the melting temperature of the pure polyamide66 membranes. By SEM, it was revealed an asymmetric morphology consisting of a skin layer and a porous sublayer, showing the pore size distribution appropriated to water-oil separation.

Abstract: The development of nanocomposites polymer matrix with clay from Brazil has been naturally abundant and low cost alternative. In this study, we obtained nanocomposites polyamide66 (PA66) with 1% and 5% of bentonite clay from Brazil, to be used as microporous organic/inorganic hybrid membranes. The clay was treated with a quaternary ammonium salt in order to make it organophilic. The membranes in the form of thin films were prepared using the technique of immersion-precipitation of solution from the nanocomposites. Treated clay and untreated clay were characterized by X-ray diffraction (XRD) and Thermogravimetry (TG). The membranes were characterized by TG and XRD. The result of XRD showed the presence of quaternary ammonium salt in the structure of clay, after organophilization. For TG, we observed that the treated clay showed higher thermal stability when compared to untreated clay. For TG, we observed that in general the membranes of PA66 with treated clay, present decomposition temperature higher when compared with untreated clay, thus revealing a greater thermal stability of membranes PA66 with treated clay. Through the X-rays patterns, it was found that membranes with 1% of nanoclay present exfoliated structure and can therefore be applied as microporous membranes.

Abstract: Bentonites are the most used fillers in the development of nanocomposites, due to their characteristics that provide nanosized particles, contributing to a large contact area between the clay and the polymer. In general, the additions of small amounts of organoclay improve the mechanical and thermal properties of nanocomposites. Bentonite clays and organoclays were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TG). The results of XRF, XRD and FTIR confirmed the presence of quaternary ammonium salt in the organoclay structure. From TG, it was observed that the organoclay showed better thermal stability when compared with bentonite clay.

Abstract: Polymers nanocomposites are a class of materials where inorganic substances with nanometrics dimensions are modified and used as dispersed loads in polymers matrices. In this work, polyamide 6.6 was chosen because of its excellent chemical, mechanical and thermal properties. The bentonite clay was treated with quaternary ammonium salt (Cetremide®) to make it organophilic and to improve the interaction with the polymer matrix. It was verified by the Torque Rheometry that the system with salt presented a bigger torque in relation to the torque of the system with untreated clay and pure polyamide 6.6. The nanocomposites presented an exfoliated and partially exfoliated structure, as evidenced by XRD. By DSC, it was observed that the treated clay increases the decomposition temperature of the nanocomposite.