Mixing, Processing, and Characterization of Bionanocomposites

One of the most important steps in the preparation of polymer nanocomposites is the mixing process. In order for the properties of a compatible nanostructured reinforcement to be fully exploited, it has to be well distributed and well dispersed. 

This is of paramount importance because reinforcement content in bionanocomposites is low and also because high surface area nanoparticles have a natural tendency to agglomerate rather than disperse in the matrix [37, 45, 58, 59, 130], Bionanocomposites can be prepared mostly by solution and melt dispersion, and in situ polymerization [20, 36, 37, 131-134]. 

Solution dispersion is a process where the nanostructured reinforcement is first dispersed in an organic solvent to allow it to swell while the polymer is dissolved in the same solvent for further mixing. Both the miifing intensity and duration is critical to ensure a good distribution and dispersion of the nanoparticles. This process has major limitations first, the polymer needs to be soluble in the same solvent used to disperse and swell the nanostractured reinforcement, and, second, solvent removal is an additional step which limits the utility of this process in large-scale industrial applications. 

In situ polymerization is a method of bionanocomposite preparation whereby the nanostructured reinforcement, usually layered clays, is dispersed in a liquid monomer or a monomer dissolved in a suitable solvent for a certain amount of time, allowing monomer molecules to diffuse between the layers. Upon further addition of initiator or exposure of appropriate source of light or heat, the polymerization takes place in situ forming the nanocomposite. 

In bionanocomposites, the reinforcement content is very low, so they can be processed by the same methods used for the pure polymers. These methods are mainly limited by the fusibility of the polymer, nature of the reinforcements, and their thermal resistance (if melt processing methods are used). The most common methods are extrusion, injection molding, casting, and compression molding, with reactive extrusion a potential option [22, 59, 123, 130]. More information 

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