Influence of chemical composition of Brazilian organoclays on the morphological, structural and thermal properties of PLA-organoclay nanocomposites

Abstract

The effects of adding different Brazilian organoclays, containing di-(hydrogenated tallow) dimethyl ammonium chloride (HTA), trihexyl tetradecyl phosphonium chloride (TDP), di(alkyl ester) dimethyl ammonium chloride (EA) and ethoxylated tallow amine (ETA), on the structure and properties of poly(lactic acid) (PLA) nanocomposites, are presented. Single and hybrid organo-modified montmorillonites (OMt and HOMt, respectively) were used to prepare nanocomposites by melt mixing in a twin screw extruder. The structural and morphological properties of the nanocomposites were evaluated using wide-angle X-ray diffraction and transmission electron microscopy. The thermal behavior was studied by differential scanning calorimetry. Fourier-transform infrared spectroscopy was used to investigate the interactions between the different organoclays and PLA. Additionally, commercial organoclays (Cloisite 30B and Cloisite 20A) were used and compared with the Brazilian organoclays. It was verified that the structure and properties of the nanocomposites highly depended on chemical composition. Comparatively, HOMt containing EA and ETA presented better compatibility with PLA, showing the best level of clay dispersion. Differential scanning calorimetry showed a dependence on the nanocomposite thermal behavior with the dispersion level of the organoclays. In general, the presence of OMt and HOMt reduced the glass transition temperature of PLA and its cold crystallization temperature, and increased its crystallinity, which was related to an effective heterogeneous crystal nucleation promoted by the organoclay