## 3 Nanocomposite Processing  
Processing of nanocomposites based on APs involves the incorporation of nanoparticles within the polymer matrix, to produce a new material, displaying a nanometric dispersion of the selected particles. Generally, a nano-homogeneous level of nanoparticles has to be achieved in order to obtain a modulation of the biopolymer properties. The primary function of the processing method is thus to guarantee an adequate nanolevel dispersion of the particles in the biopolymer matrix, with a structural integrity of the nanoparticles. Furthermore, important points are also to avoid the adverse effects on the polymer. A variety of processing techniques can be exploited to develop dense polymer nanocomposite films [10; 11; 12; 13; 8; 64] or three-dimensional porous structures [65; 66]. The selection of the processing method depends on the type of biopolymer, on the nanoparticle, and the final application. The incorporation of micro- and nanostructures into polymer can be done in different ways that can be generally divided in:  
* Solvent casting methods
* Melt mixing methods  
Solution methods involve dissolution of the polymer matrix in an appropriate solvent with nanoparticles followed by either solvent evaporation or precipitation. The polymer solvent casting method represents a low-cost and rapid strategy, widely used for the processing of flexible biopolymer blend and bio-nanocomposite films for various applications [67]. The polymer is typically dissolved in a specific solvent while the nanoparticles are dispersed in the same or in another solvent; afterwards, the two parts are mixed together. The effect of solvent in the film processing and in the material properties is a key point that needs to be elucidated. Indeed, the selected solvent influences the film properties, in terms of thermal, mechanical, and surface properties, of homogeneity of the surface micro and nano-structure, reorientation or mobility of the surface crystal segment, swelling, and deformation [10; 11; 12; 13; 38; 64; 68]. Polymer solubility is one of the main points to analyze and study in terms of temperature dependence and the solubility limit. The interfacial adhesion between the polymer and the nanoparticles and the solvent casting mixing conditions during fabrication of biopolymer-based films strongly affect the network structure of the film, physical and chemical properties, and final film performance. The solution with biopolymer based blends or bio-nanocomposite is finally deposited in an open mold until complete evaporation. Furthermore, the evaporation conditions, in terms of humidity, temperature, and pressure strongly affect evaporation rate of the solvent, that it is strictly related with the obtained surface morphology. Furthermore, in the casting process, the film quality is strongly related to the rheological behavior of the film-forming solution. Solution mixing has been widely used in order to produce nanocomposites based on carbon nanostructures as CNTs or graphene. However, these materials are very cohesive due to Van der Waals bonds between the carbon atoms. Achieving the desired dispersion is not easy in the liquids owing to their strong tendency for agglomeration; hence, in order to reduce the agglomeration and to obtain nanofiller dispersion in a liquid, an ultrasonication process is generally applied. First, the polymer matrix and the fillers are dissolved in a solvent and (only at this stage) the filler solution is exposed to ultrasonication. After, the two solutions are mechanically mixed together until a homogenous mixture is achieved. Finally, the solvent is evaporated from the suspension [10; 11; 12; 13; 38; 64; 68]. The processing of polymer nanocomposites (PNs), based on thermoplastic polymer matrices by conventional polymer melt compounding methods represents a promising approach to obtain a good nanoparticle dispersion and to greatly expand the commercial opportunities for this technology.