Preparation and Processing of Biodegradable Polymer Nanocomposites

Intercalation/exfoliation of biodegradable polymer macromolecules in layered hosts, such as layered silicates, has been proved as an effective method to synthesize polymer layered silicate nanocomposites. Methods like solution intercalation, in-situ synthesis and melt intercalation have emerged as successful methods to prepare biodegradable polymer layered silicate nanocomposites. 

Solution intercalation is based on a suitable solvent system in which the polymer is soluble and the silicate layers are easily swellable. Prior to the nanocomposite preparation biodegradable polymer is allowed to dissolve in a suitable solvent. The same solvent is used to disperse nanoclays through optimized cycle of mechanical stirring and sonication process. Futher, both solutions are mixed through a coupled process of mechanical stirring and sonication. The cycle time and order depends upon the nature of the matrices and fillers and also the composition. A similar mechanical stirring and sonication coupled process has been used by Miyagawa et at 

In this method, the layered silicate is allowed to disperse within the liquid monomer or a monomer solution so that the polymer formation can occur between intercalated layers of the nanoclay. Polymerization can be initiated either by heat or radiation, by the utilization of a suitable initiator, or by an organic initiator or catalyst fixed through cation exchange inside the interlayer before the swelling step [32]. 

However, in the case of biopolymers the processing window observed was very narrow, which in general lays in between the melting and degradation point of the material. For PLA the processing temperature observed was in between 175-190°C imder a screw speed of 40-60 

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