Preparação de nanocompósitos de poli (tereftalato de etileno) bentonita.

Abstract

This work deal with the obtaining of nanocomposites of poly(ethylene terephtalate) (PET)/bentonite prepared by melt intercalation. To obtaining the nanocomposites, bentonite clay (ASCN) was modified chemically through chemical reaction with quaternary ammonium salt of commercial name, Cetremide and designated by ASCM. As comparison parameter it was used a commercial organophilic bentonite clay, Cloisite 30B. These clays were characterized by chemical analysis, cation-exchange capacity (CEC), infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetry (TG). The results of these analyzes showed that the organic salt was incorporated between the layers of clay producing an organophilic clay. Masterbatches (1:1) PET/unmodified bentonite, PET/ASCN, organically modified bentonite, PET/ASCM and commercial organoclay, PET/Cloisite 30B, PET/CL, were prepared using the internal mixer of a Haake torque rheometer operating at 260 °C and 60 rpm for 10 min. The masterbatch was then mixed with PET in appropriate amounts to obtain composites contents of 1 - 3 wt% clay. These were processing in a counter-rotating twin-screw extruder connected to the Haake rheometer and operating at 275 °C and 60 rpm and then injection molded on a Fluidmec injection machine. The compounds obtained were coded by PET/ASCN, PET/ASCM and PET/CL with 1 - 3 wt% clay. The samples were mechanically tested and characterized by XRD, TG, differential scanning calorimeter (DSC) and scanning electron microscopy (SEM). The results from XRD and SEM for the three compounds indicated a non insertion of the polymer molecules between clay lamella and therefore, the obtaining of materials with microcomposite structure. The values of TG showed that the thermal properties of the compounds were affected by the content and organophilization of the clay, showing higher thermal stability for the compound, PET/ASCM. The results from DSC presented thermal transitions unaffected for the compositions containing unmodified clay, PET/ASCN, as for the samples with organoclays, PET/ASCM and PET/CL. Best values of impact strength was obtained for the compound, PET/CL, especially containing 3 wt% of clay.