Application of a constitutive model to extensional and shear rheology of polystyrene carbon nanofiber composites
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Publisher:The Ohio State University
Series/Report no.:The Ohio State University. Department of Chemical and Biomolecular Engineering Honors Theses; 2015
This research focuses on improving an existing constitutive model to predict the rheology of polystyrene-carbon nanofiber (CNF) composites and examining the differences between two nanocomposite preparation techniques and two types of nanofibers. The constitutive model is a set of equations adapted to predict the dynamic behavior of polymer nanocomposites and the orientation evolution of nanofibers. The equations in the model are functions of time, type of flow, stress, deformation, nanofiber orientation, and flow history due to the polymer's viscoelasticity. Important parameters in the model include: polymer relaxation time, polymer viscosity, mobility factor, polymer-particle interaction, particle-particle interaction, and aspect ratio. Three flow fields were examined: small-amplitude oscillatory shear, transient shear, and transient extensional flows. The two preparation techniques examined are commonly used in preparing polymer composites: melt-blending and solvent casting. The nanofibers examined were as received from the manufacturer with some undergoing additional high-heat treating. This research resulted in the development of an accurate model for the composites for all three flow fields. Values of parameters in the model have given insight into the physical behavior of the composite due to polymer-particle and particle-particle interactions and due to agglomeration. An accurate model of a polymer-CNF composite would be beneficial to industry, as the manufacturing processes such as extrusion, flow through dies, or spraying alter the orientation and consequently the mechanical, electrical, thermal, and optical properties of the composite. This model can provide a way to understand these effects would improve the optimization of properties.
Academic Major: Chemical Engineering
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