Shear and Extensional Rheology of Nanoclays and Nanotubes in Polymer Melts and Solutions

Ohio State University Research Foundation -Do Not Use, Columbus OH

Investigators

Abstract

This grant provides funding for the comprehensive characterization of the non-linear rheology, particle orientation, and structure development of nanoclay/polymer and carbon nanotube/polymer composites, in both shear and elongation, and the development of simulation tools for control and optimization of processes for nanocomposites. Polymer nanocomposites exhibit significantly enhanced performance properties, including increased strength, stiffness, barrier properties, and heat resistance, without a significant loss in impact strength. Two types of nanoparticles, naturally occurring layered nanoclays and synthesized carbon nanotubes, show promise in improving the mechanical and electrical properties of thermoplastic and thermoset polymers. However, these improvements come with a cost in processing: small additions of the high surface-area-to-volume-ratio nanoclays and nanotubes have been observed to significantly increase the viscosity and elasticity of polymer melts and solutions, complicating the extrusion and injection molding of polymer nanocomposite products. In addition, the effect of processing on nanoparticle orientation and structure development, and hence performance properties of the product materials, is not well understood. With the proposed comprehensive rheological and structural characterization of polymer nano-composites, questions such as the following will be addressed: What are the shear and extensional viscosities of melts and solutions filled with extremely large aspect ratio nanoparticles? What are their dependencies on nanoparticle geometry, varying between tubes and discs of different aspect ratios? What is the particle orientation and structure development in shear and extensional flow? What models can be developed for process modeling of stress/strain/structure? To what degree do nanoparticles become aligned in an extensional flow? What are the correlations between elastic properties of nanotubes and nanoclays and the viscoelasticity of the polymer melts and solutions, between nanoparticle concentration and viscoelastic properties of solutions, between orientation and structure development and viscoelastic properties? What are the flow-aligning properties of the nanoparticles in extension and shear, and do the tubes and platelets have very different flow-aligning structures?