(50a) Melt Shear and Extensional Rheology of Carbon Nanofiber/Polystyrene Composites

There has been much interest in carbon nanofiber (CNF) based polymer nanocomposites in recent years because CNFs have the potential to create materials with enhanced mechanical, thermal, and electrical properties using much lower particle loadings than conventional microscale fillers such as carbon black, carbon fibers, and glass fibers, and CNFs are considered less of a health hazard than carbon nanotubes. It is well known that the physical properties of the nanocomposite are greatly dependent upon the nanoparticle orientation developed during processing and the dispersion of the particles within the polymer matrix however there have been few studies of the qualitative and quantitative rheological behavior of nanocomposites containing CNFs. Thus a greater understanding of the rheological behavior of polymer/CNF composites both qualitatively and quantitatively while accounting for factors such as particle size, shape, concentration, and interactions with the polymer, and the evolution of particle orientation during processing flow is needed. This knowledge will allow for the creation of models that have the ability to predict the flow properties of polymer nanocomposites and the orientation changes of the nanoparticles during flow which is necessary for the design of manufacturing processes that optimize desired performance properties.

We have investigated the rheological behavior of melt phase polystyrene (PS)/CNF composites under transient shear and extensional flows, and in this work we analyze in detail the transient shear and transient extensional viscosity measurements, measure the changes in the nanostructure that occur during shear and extensional flow using transmission electron microscopy and discuss the rheological behavior of PS/CNF composites in terms of weight fraction, CNF length and type of CNF.