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Effects of carbon nanotubes (CNT) on the dynamic mechanical property, thermal property, and crystal structure of poly(L-lactic acid) (PLLA) were investigated. Dynamic mechanical analysis (DMA) found that CNT via grafting modification with PLLA (CNT-g-PLLA) could result in effective reinforcing effects. Tan d of DMA found that CNT-g-PLLA was compatible with the PLLA matrix, giving a single T g of the composite with a higher CNT-g-PLLA loading giving a higher T g of the composite. Wide angle X-ray diffraction (WAXD) data demonstrated that CNT could assist the disorder-to-order (a 0 -to-a) transition in PLLA crystals but did not lead to a more compact chain packing of the crystal lattice in PLLA composites than in pure PLLA. The equilibrium melting temperature (T 0 m ) obtained from Hoffman-Weeks plots were found to increase with increasing CNT-g-PLLA content. Small angle X-ray scattering data revealed that thicknesses of crystal layer and amorphous layer of PLLA both decreased with increasing CNT contents. V C 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: [145][146][147][148][149][150][151][152] 2010

Effects of carbon nanotubes (CNT) on the isothermal crystallization kinetics of poly(L‐lactic acid) (PLLA) were quantitatively investigated using the Avrami equation and the secondary nucleation theory of Lauritzen and Hoffman. CNT via grafting modification with PLLA could well disperse in the PLLA matrix and give significantly enhanced crystallization rate and crystallinity of PLLA as analyzed by differential scanning calorimetry and polarized optical microscopy. Analysis of isothermal crystallization kinetics using the Avrami equation demonstrated that CNT significantly enhanced the bulk crystallization of PLLA. Analysis of spherulite growth kinetics using the secondary nucleation theory of Lauritzen and Hoffman found that CNT could expand the temperature range of the crystallization regime III of PLLA. Values of the nucleation constant (Kg) in crystallization regimes III and II of PLLA both increased with increasing CNT contents. The Kg III/Kg II ratios were found to be close to the theoretical value 2 but were not clearly found to depend on the CNT contents. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 983–989, 2010