PLA-based nanocomposites filled with the commercial organomodified montmorillonite Dellite 43B (D43B) and containing acetyl tri-n-butyl citrate (ATBC) as plasticizer were prepared by extrusion in a pilot-scale twin-screw extruder and melt casted into flexible films. A preliminary investigation was carried out in a laboratory batch mixer by varying blending conditions and addition procedures of the components. Indeed, the method of addition of ATBC and D43B considerably affected thermo-mechanical properties and morphology of the resultant nanocomposites. The simultaneous introduction of both ATBC and D43B during the extrusion process allowed producing clearly exfoliated nanocomposite materials with modulated mechanical and thermal properties. Moreover, rheological results, obtained during melt extrusion, assessed the processability of nanofilled-plasticized PLA, making this simple procedure interesting in view of the industrial production of nanostructured biomaterials based on plasticized PLA.

The present article is focused onto the study of nanostructure, thermal and mechanical properties of nanocomposites composed of poly(lactide) (PLA), and a constant amount of montmorillonite (MMT) clays (3 wt %). Properly modified organoclays with easily available commercial compounds were prepared in order to allow the homogeneous dispersion of the hydrophilic clays in the polar polymer matrix; in particular, 2-hydroxyethyl-trimethylammonium (choline), polyethyleneoxide(15)-(hydrogenated tallow)-ammonium, and oligochitosan salts were used as surfactants as their structure can match the requirements of a biocompatible material. These organi-cally modified MMTs (OMMTs) were used for preparing composites by melt blending or by in situ ring opening polymerization (using the clay surfactant as polymerization initiator) followed by melt dispersion into a PLA matrix. Structural, morphological, and thermo-mechanical properties of the products are compared in order to assess advantages and disadvantages of the two different preparation routes. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 125: E413-E428, 2012 Cloisite 30 B Dimethyl, benzyl, hydrogenated tallow, quaternary ammonium montmorillonite HT is Hydrogenated Tallow Cloisite 10A Dellite 43B Dimethyl, dehydrogenated tallow, 2-ethylhexyl quaternary ammonium montmorillonite Cloisite 25A Methyl, dehydrogenated tallow, quaternary ammonium montmorillonite Cloisite 93A Dimethyl, dehydrogenated tallow, quaternary ammonium montmorillonite Cloisite 20A (0.95 mg/g clay) Cloisite 15A (1.25 mg/g clay) Cloisite 6A (1.4 mg/g clay) Dellite 72T E414 CASTIELLO ET AL.

Although the improvement of tensile Modulus and thermal stability due to the addition of innovative organoclays to PLA were negligible, our investigation allowed to evidence that the preliminary preparation of an inorganic rich composite through in situ polymerization of lactyde gave a final morphology improved with respect to that achieved by simply melt dispersing organoclay powder. Anyway the former preparation method should be further investigated in order to control PLA structural features resulting from the ring opening polymerization synthesis