Desenvolvimento de membranas assimétricas de nanocompósitos de poliamida 6/argila por inversão de fases.

Abstract

Asymmetric microporous membranes were prepared by precipitation immersion technique, from polyamide 6 nanocomposites with national clays. The clay was used as non-treated (MMT) and treated (OMMT) with ammonium quaternary salts. To confirm the presence of the salt groups of chemicals in the clay, it was done the test with X-ray diffraction (XDR) and X-ray fluorescence (XRF). After, it was prepared a master of PA 6/clay in the proportion of 1:1 and added to a polyamide 6 matrix in a counter-rotating twin-screw extruder, with clay content of 3 and 5% in weight. The nanocomposites were characterized by XRD, thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). From the results of XRD it was observed a morphological structure with lamellae of clay exfoliated/partially exfoliated in the PA 6 matrix. Also the nanocomposite presented thermal stability and in general the presence of clay does not cause significant change in the crystallinity of polyamide 6. The membranes were prepared by phase inversion technique, changing the synthesis conditions and it was characterized by XRD, DSC and scanning electron microscopy (SEM). The XRD patterns from the membranes show indicated a structure that is in accordance with the results obtained to nanocomposites. From DSC it was observed that there was no significant change in the crystallinity with the presence of clay. Also it was observed from DSC and from DRX the presence of two crystalline phases of PA 6 for all compositions. From SEM it was showed an asymmetric morphology, consisting of skin film and a porous layer for all membranes. The content of polymer solution, presence of clay and the use of successive exchanges of non-solvent cause changes in the morphology of the membranes and in the pore formation. From wetting test and mercury porosimetry it was observed that the presence of clay changes the wetting and significantly reduced the average pore diameter of the membranes.