New polylactide/layered silicate nanocomposites: Role of organoclays

In the preparation of polymer/clay nanocomposites, organoclay plays an important role in lipophilizing and dispersing the clay into less polar polymer matrixes. Organic modifiers of various chain lengths were examined in different types of clays, smectite, montmorillonite (MMT), and mica, to prepare their corresponding organoclays. The layered structure and gallery spacing of organoclays and polylactide (PLA) nanocomposites shows that, with a modifier of the same chain length, the gallery spacing of the organoclay was largest for mica and smallest for smectite because of the higher ion-exchange capacity of mica and physical jamming of the modifier due to a restricted conformation at the core part of the clay of larger size. The increment of the modulus in a smectite nanocomposite, compared to that of PIA, is higher than MMT or mica nanocomposite due to better dispersion in a smectite system for the same clay loading. Being a well-dispersed system, smectite nanocomposites have better gas barrier properties than the MMT or mica systems, which are larger in size but stacked in nature in their nanocomposites. A new idea for obtaining porous ceramic material from layered silicate/polymer nanocomposites by burning is unveiled using various clays and the mechanism of their formation is elucidated.