Structure, Thermal Stability, and Mechanical Modulus of Polylactide Nanocomposites Reinforced with Organically Modified Layered Silicate

Abstract

We have manufactured polylactide (PLA) nanocomposites reinforced with layered silicates by the melt compounding method and have investigated their structure, thermal stability under oxygen or nitrogen atmosphere, and temperature-dependent mechanical modulus by adopting XRD, SEM, TGA, and DMA. Octadecylammonium-modified montmorillonite (organo-MMT) is used as an organically modified layered silicate and, for comparison, sodium montmorillonite (Na-MMT) is adopted as a purely inorganic layered silicate. X-ray diffraction patterns and SEM images confirm that the organo-MMT is intercalated and dispersed homogenously in the PLA matrix, whereas Na-MMT remains unchanged by forming agglomerated domains in the matrix. Unlike the PLA/Na-MMT nanocomposites, the thermal stability of PLA/organo-MMT nanocomposites is found to be substantially improved with the increment of organo-MMT content, especially under oxygen gas atmosphere. In addition, the mechanical modulus of PLA/organo-MMT nanocomposites in the glassy state are highly improved.