Poly(lactic acid)/clay nanocomposites: effect of nature and content of clay on morphology, thermal and thermo-mechanical properties

Nanocomposites were prepared by melt blending Poly(lactic acid) with 5 and 7 wt% of an organically modified montmorillonite or an organically modified magnesium sodium fluoro-hectorite or unmodified sepiolite. All nanocomposites show a good level of clay dispersion into the polymer matrix as well as a considerable thermal and thermo-mechanical properties improvement. According to thermal analysis, the clays seem to act as nucleating agents inducing a higher degree of crystallinity of the polymer and rate of crystallization. Similar increases in the thermal stability of Poly(lactic acid) were obtained for all clays. Concerning layered silicate nanocomposites, it was found that the main influencing factors on the thermo-mechanical.properties appear to be the aspect ratio and dispersion of clay nanoplatelets, rather than polymer/clay chemical compatibility. Needle like sepiolite shows thermo-mechanical improvements comparable to some layered silicates and an interesting ability to maintain high storage modulus values at increasing temperatures, due to its good dispersion within the polymer without the need of organic modifiers as instead necessary for layered clays used in this work. (C) 2012 Elsevier B.V. All rights reserved.