Processing, structure and properties of semi-crystalline polymer nanocomposites

Semi-crystalline polymers are of technological and commercial interest in areas ranging from aerospace materials to biomedical applications to sensors and actuators. In many cases researchers are seeking to add various nanoparticles to impart multifunctionality and enhanced properties to the polymer system. However, the addition of carbon nanotubes (CNTs) and other nanoparticles can greatly alter the resulting crystallization kinetics and crystalline morphology of semi-crystalline polymer nanocomposites. For example, when melt-processing semi-crystalline polymer nanocomposites, the nanoparticles can act as nucleating agents and can significantly alter (and in many cases accelerate) the processing-induced crystallization behavior of the nanocomposite samples. Here such changes were found to be a function of a number of parameters including the polymer type, the size and shape of the nanoparticle, the chemistry of the nanoparticle surface, and the processing parameters. Alternatively, when working with solutions of semi-crystalline polymers in the presence of CNTs, it was found that CNTs can be coated (functionalized) with small polymer crystals, with the crystal size found to depend on the polymer concentration. Here under certain processing conditions the resulting polymer morphology shows a periodicity resembling the nano-hybrid shish-kebabs (NHSKs) microstructure. Lastly, solution crystallization was utilized to prepare nylon-11 nanocomposites in order to study the influence of processing (uniaxial drawing) and resulting microstructure on nanocomposite effective properties. The results obtained suggest that enhancements in functional properties of semi-crystalline polymer nanocomposites depend not only on addition of nanoparticles but can also be achieved by control of the processing parameters and the resulting changes in nanocomposite microstructure.