Comparative study of poly(L-lactide) nanocomposites with organic montmorillonite and carbon nanotubes

Organic montmorillonite (OMMT) and the one-dimensional functionalized multiwalled carbon nanotubes (FMWCNTs) were introduced into poly(L-lactide) (PLLA) to prepare PLLA/OMMT and PLLA/FMWCNT nanocomposites, respectively. The effects of nanofillers on melt crystallization and cold crystallization of PLLA were comparatively investigated by using polarized optical microcopy, differential scanning calorimetry and wide angle X-ray diffraction. The results show that FMWCNTs exhibit higher nucleation efficiency for the melt crystallization of PLLA, whereas OMMT is the better one for the cold crystallization of PLLA. Rheological properties show that both OMMT and FMWCNTs at relatively higher concentrations can form the percolated network structure in the PLLA matrix, however, the latter nanocomposites exhibit relatively denser or more compact percolated networks. The difference of the networks between OMMT and FMWCNTs is suggested to be the main reason for the different cold crystallization behaviors observed in the PLLA/OMMT and PLLA/FMWCNT nanocomposites. The dynamic mechanical analysis measurements show that OMMT is the better one to improve the stiffness of the nanocomposites in the present work. The thermogravimetric analysis measurements show that FMWCNTs have higher efficiency in improving the thermal stability of PLLA compared with OMMT. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013