Thermal and mechanical properties of plasticized poly(L-lactide) nanocomposites with organo-modified montmorillonites

Nanocomposites of poly(lactide) (PLA) and the PLA plasticized with diglycerine tetraacetate (PL-710) and ethylene glycol oligomer containing organo-modified montmorillonites (ODA-M and PGS-M) by the protonated ammonium cations of octaclecylamine and poly(ethylene glycol) stearylamine were prepared by melt intercalation method. In the X-ray diffraction analysis, the PLA/ODA-M and plasticized PLA/ODA-M composites showed a clear enlargement of the difference of interlayer spacing between the composite and clay itself, indicating the formation of intercalated nanocomposite. However, a little enlargement of the interlayer spacing was observed for the PLA/PGS-M and plasticized PLA/PGS-M composites. From morphological studies using transmission electron microscopy, a finer dispersion of clay was observed for PLA/ODA-M composite than PLA/PGS-M composite and all the composites using the plasticized PLA. The PLA and PLA/PL-710 composites containing ODA-M showed a higher tensile strength and modulus than the corresponding composites with PGSM. The PLA/PL-710 (10 wt %) composite containing ODAM showed considerably higher elongation at break than the pristine plasticized PLA, and had a comparable tensile modulus to pure PLA. The glass transition temperature (T-g) of the composites decreased with increasing plasticizer. The addition of the clays did not cause a significant increase of T-g. (c) 2005 Wiley Periodicals, Inc.