Renê Anísio da Paz

Polyamide 66/Brazilian clay nanocomposites

Polyamide 66 (PA66)/Brazilian clay nanocomposites were produced via direct melt intercalation. A montmorillonite sample from the Brazilian state of Paraiba was organically modified with esthearildimethylammonium chloride (Praepagen), quaternary ammonium salt and has been tested to be used in polymer nanocomposites. The dispersion analysis and the interlayer spacing of the clay particles in matrix were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal behavior of the obtained systems was investigated by differential scanning calorimetry (DSC), thermogravimetry (TG), and heat deflection temperature (HDT) was reported too. The nanocomposites exhibited a partially exfoliated structure, very interesting HDT values which are higher than those of pure PA66, and good thermal stability.

Structure and mechanical properties of polyamide 6/Brazilian clay nanocomposites

Recent interest in polymer/organoclays nanocomposites systems is motivated by the possibility of achieving enhanced properties and added functionality at lower clay loading as compared to conventional micron size fillers. By adding montmorillonite clay to polyamide 6 increases the Young modulus, yield strength and also improves barrier properties. In this work, nanocomposites of polyamide 6 with montmorillonite clay were obtained. The clay was chemically modified with three different quaternary ammonium salts such as: Dodigen, Genamin and Cetremide. In this case, a dispersion of Na-MMT was stirred and a salt equivalent to 1:1 of cation exchange capacity (CEC) of Na-MMT was added to the dispersion. The montmorillonite clay (untreated and treated by ammonium salts) and nanocomposites were characterized by X ray diffractions. Also the nanocomposites were characterized by transmission electron microscopy and mechanical properties. The results indicated that all the quaternary ammonium salts were intercalated between the layers of clay, leading to an expansion of the interlayer spacing. The obtained nanocomposites showed better mechanical properties when compared to polyamide 6. The clay acted as reinforcing filler, increasing the rigidity of nanocomposites and decreasing its ductility.

Nanocompósitos de poliamida 6/Argila organofílica: efeito do peso molecular da matriz na estrutura e propriedades mecânicas e termomecânicas

Polyamide 6/organoclay nanocomposites were prepared by the melt intercalation technique. The clay was treated with a quaternary ammonium salt (Genamin) to obtain the organoclay (OMMT), being characterized by X ray fluorescence (XRF) and X ray diffraction (XRD). The results confirmed the incorporation of the salt into the clay structure, i.e. the organophilization. The nanocomposites were obtained with a counter-rotational twin screw extruder with 3 wt.% of clay and characterized by XRD, transmission electron microscopy (TEM), tensile testing, dynamical-mechanical thermal analysis (DMTA) and heat deflection temperature (HDT). The XRD and TEM results showed exfoliated and/or partially exfoliated structures. The tensile properties were superior to those of the pure polyamide 6.The analysis with DMTA and HDT also showed that the incorporation of the organoclay into the polymer matrix increased the rigidity (storage modulus) of the system, confirming the reinforcing effect of the clay on the polymer.

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.

Influence of Processing Type in the Morphology of Membranes Obtained from PA6/MMT Nanocomposites

The nanocomposites have an extensive use in the current process of membrane preparation, taking into account their unique features as membranes. Thus, the study of nanocomposite processing to obtain membranes is highly important. In this work, Brazilian clay was used (Brasgel PA) for the preparation of polyamide/clay nanocomposite. The nanocomposites were produced in a high rotation homogenizer and in a twin screw extruder. From the nanocomposites and pure polymers processed in the two equipments, membranes were prepared by the immersion-precipitation method, using formic acid as solvent. By X-ray diffraction (XRD), the formation of exfoliated and/or partially exfoliated structures with changes in the crystalline phases of the polyamide was observed. From scanning electron microscopy images, it was observed that the processing clearly influenced the membrane morphology.

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.

Membranes from Nylon 6/Regional Bentonite Clay Nanocomposites

In this work, it was produced hybrids organic/inorganic membranes of nylon6 and clay mineral constituted of silicate layers, from the interior of the Paraiba. The sodic clay was used in the untreated and treated (with quaternary ammonium salts) form (to become compatible with polymer). Commercial salts Genamin and Cetremide were used to prepare organoclay by cationic exchange reaction in aqueous phase. The nanocomposites were obtained by melt intercalation and from these nanocomposites it was synthesized the membranes for dissolution in predetermined amounts of formic acid and a precipitation in a non-solvent, also called immersion-precipitation technique to prepare thin films. Thus, on the basis of the results, it can be observed that the presence of the treated and untreated clay confer a significant alteration in the structure/morphology of the pores and the porosity of the membrane.

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%.