Paper Number
SC31 

Session
Suspensions & Colloids

Title
Shear-induced microstructural evolution and implications for the rheo-dielectric behavior of carbon black suspensions

Presentation Date and Time
October 17, 2018 (Wednesday) 11:30

Track / Room
Track 1 / Galleria I

Authors (Click on name to view author profile)

  1. Hipp, Julie B. (University of Delaware, Chemical and Biomolecular Engineering)
  2. Richards, Jeffrey J. (National Institute of Standards and Technology, NCNR)
  3. Wagner, Norman J. (University of Delaware)

Author and Affiliation Lines (in printed abstract book)
Julie B. Hipp1, Jeffrey J. Richards2, and Norman J. Wagner1
1University of Delaware, Newark, DE; 2NCNR, National Institute of Standards and Technology, Gaithersburg, MD 20899

Speaker / Presenter 
Hipp, Julie B.

Text of Abstract
The shear-induced behavior of carbon black suspensions is highly relevant due to the widespread use of these materials in applications where flow is an important aspect of processing and end use. In these applications, macrosopic properties such as the viscosity and electrical conductivity of the suspension are key design parameters that are ultimately determined by the suspension microstructure. While much research has been aimed at understanding the relationship between the microstructural and macroscopic properties of carbon black dispersed in a variety of media including oils, polymers, and alkyl carbonates, a direct measurement of the structure of these suspensions while under shear has been challenging. In this work, a Rheo-USANS (Ultra-Small Angle Neutron Scattering) instrument is used to measure the shear-induced microstructure and resulting macroscopic rheological response of a commercially available conductive carbon black, Vulcan XC-72, suspended in Newtonian fluids. The shear-induced dielectric properties of these suspensions are measured and directly related to the observed microstructural evolution from Rheo-USANS measurements. These experiments confirm that the shear-thinning behavior commonly observed in these suspensions arises due to the erosion of carbon black agglomerates with increasing shear rate. The effect of shear is also observed in the electrical properties where upon yielding, a system-spanning network of inter-agglomerate bonds is broken and a consequent decrease in electrical conductivity is observed. With increasing shear rate, however, the observed structural erosion gives rise to different trends in conductivity depending on the suspending medium. Both the rheological and electrical consequences of the flow-induced microstructure of this suspension have implications for the design and improvement of many technologies including energy storage devices, inks, and polymer composites.