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Carbon nanotubes have exhibited unusually large changes in selective physical and mechanical properties when added to polymers or polymer composites in small quantities. To understand their rheological behavior and processibility, we mixed multiwalled carbon nanotubes (MWNT) in epoxy and created suspensions of different dispersion qualities, MWNT aspect ratios, concentrations, suspension network structures, and MWNT orientation states. Their rheological properties were measured with a cone and plate rheometer. It was found that as MWNT dispersion quality improved or their network connections, the aspect ratio or concentration increased, the MWNTs interactions became stronger as indicated by a higher storage modulus G′, complex viscosity ∣η*∣, and steady shear viscosity η. It was found that suspensions which contained a mixture of separated MWNT along with small MWNT aggregates exhibited G′ that was independent of frequency suggesting solidlike behavior. This frequency sweep method could be used to characterize the network structure state for well dispersed nanotube suspensions. The steady shear viscosity η was found to be more sensitive to MWNT separation than G′ and ∣η*∣. All suspensions exhibited shear thinning behavior and nanotubes showed statistically significant alignment in the direction of the shear flow. Aligned MWNT suspensions not only displayed lower η than randomly orientated MWNT suspensions, but also had lower G′ and ∣η*∣ values. Transmission electron microscope (TEM) images of cured suspensions and a recently developed capillary method was used to validate the MWNTs suspension state and its microstructure.

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This chapter will report on the progress of various researchers in addressing the key challenges in manufacturing polymer nanocomposites with carbon nanotubes. Unique properties of the carbon nanotubes (CNT) offer the potential for them to serve as excellent reinforcements for advanced nanocomposites with better mechanical and multi functional properties. One critical step that will affect the outcome is the processing method and approach that is used to manufacture such CNT/Polymer composites. The processing method will influence the final micro structure of CNT in the composite which determines the CNT effectiveness in the nanocomposite. This chapter will focus on reviewing the current state of research on CNT dispersion, interfacial bonding between the CNT and the polymer matrix, and CNT orientation during flow. All these parameters influence the evolution of the microstructure and hence play a key role in tailoring the properties of the polymer nanocomposites.