Efeito do peso molecular da poliamida 6 no desenvolvimento da nanocompósitos.

Abstract

The effect of polyamide 6 (PA6) molecular weight on the development of polymer/layered silicates nanocomposites prepared by the melt intercalation technique was studied in this work. The clay was treated with a quaternary ammonium salt (Genamin) to obtain the organoclay (OMMT). It was characterized by X-ray fluorescence (XRF), Fourier Transform infrared spectroscopy (FTIR), thermogravimetry (TG) and X-ray diffraction (XRD). The results of these analyses showed the incorporation of the salt in the clay structure, confirming the organophilization. In order to obtain the polyamide 6/organoclay nanocomposites masters of PA6: organoclay (1:1) were prepared to facilitate the mixture in the counter-rotational twin screw extruder. The obtained masters were incorporated in the polymer matrix at a content of 3 wt.% of clay and then, the pellets were injected using a Fluidmec injection molding machine. The materials were characterized by torque rheometry, melt flow index, Fourier Transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), mechanical properties (tensile and Izod impact strength), heat deflection temperature (HDT) and dynamical-mechanical thermal analysis (DMTA). The results of torque rheometry and melt flow index showed that the presence of organoclay in the polyamide 6 increased the torque in relation to the untreated clay and, the bigger the shear rate the smaller the viscosity of the material, confirming the pseudoplastic behavior of the system. The patterns of XRD of the films of PA6/organoclay showed that all systems presented predominance exfoliated structure which was confirmed by TEM. However, the results of XRD and TEM of the specimens obtained by injection molding showed exfoliated and/or partially exfoliated structure. The crystallinity degree of nanocomposite obtained by DSC, its mechanical properties of tensile and HDT were enhanced in relation to pure PA6. In general, the polyamide 6 with high molecular weight nanocomposites presented more significant results of these properties. On the other hand, its Izod impact strength was reduced. The DMTA analysis showed that the incorporation of organoclay in the polymer matrices increased the rigidity (E*) of the system and the tanS decreased for all studied temperatures, confirming the reinforcing effect of the clay in the polymer. Hence, one can say that the systems with high molecular weight polyamide 6 presented better properties in relation to the ones with lower molecular weight.