Materials and Methods for Reactive Molding of Nanocomposites

In-situ intercalative polymerization of layered silicates is perhaps the best example of reactive molding of nanocomposites today. In-situ interactive polymerization of layered silicates, which was discussed above, can be achieved either with thermosetting matrices, such as polyurethane and epoxy, or with thermoplastic systems, such as nylon-6 [4, 23]. A general requirement for reactive molding of nanocomposites is that the particulate phase of a PNC is compatible with the monomer phase of the reactive molding system, which acts as a polymerizable solvent This makes it possible to achieve and maintain a fine dispersion of the particulate phase in the monomer during matrix consolidation, resulting in excellent particle distribution in the final PNC. Above, it was noted that the hydroxylated surface of cellulose makes it reactive to isocyanate. Cellulose whiskers may therefore represent the ideal particulate phase for a nano-RIM process. For this to be achieved, the whisker-polyurethane system needs to be better characterized, so that the RIM process can be adapted to fabrication of cellulose whisker PNCs. 

Stereolithography, which has also been referred to as UV-RIM (i.e., ultraviolet light induced reaction injection molding), is a second reactive molding process, which has found appUcation in rapid prototyping [60, 61]. The low viscosity of a U V-RIM resin should also be conducive to achieving a dispersion of nanoparticles in the PNC matrix. 

Although a range of reactive monomers could be selected for reactive molding of polymer nanocomposites, bio-based monomers with the potential to replace materials traditionally derived from the petrochemical supply chain are of particular interest today. On the one hand, the Technology Roadmap for Plant/Crop-Based Renewable Resources 2020 (sponsored by the U.S. Department of Energy), calls for 10% of basic chemical building blocks to be plant-derived by 2020 [16]. 

On the other hand, the Forest Products Industry s Agenda 2020 identifies the critical importance of nanotechnology in the development of new generations of high-value, high-performance materials from forest-based products that would compete favorably with the properties of conventional, petroleum-based materials. 

One such polymerizable solvent-monomer, which satisfies these various requirements for a reactive molding system, is FA. 

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