Chemistry Reference
In-Depth Information
Chapter 2
R
HEOLOGY OF
C
ARBON
B
LACK
S
USPENSIONS
Yuji Aoki
Department of Polymer Science and Engineering,
Yamagata University, Yonezawa, Yamagata, Japan
Abstract
This article gives a review of the rheology of carbon black (CB) suspensions.
Extensive studies have been made for the CB suspensions. However, a large
fraction of these studies was devoted for the suspensions in fairly non-polar
media where the CB particles having the polar surface. The rheological
properties of CB suspension are affected by the medium affinity to the CB
particles. Different types of rheological behavior are observed accordingly, when
the affinity changes. In the medium having a low affinity, the CB particles form
the continuous network-type agglomerate and exhibit a strong nonlinearity
attributable to strain-induced disruption of a fully developed three-dimensional
(3D) network structure of the CB particles therein characterized by the yield
stress. In contrast, in the medium having a moderate affinity, the suspensions
show a sol-gel transition with increasing CB concentration, and the critical gel
behavior characterized with a power-law relationship between the modulus and
frequency (), G G/tan(n/2)
n
is observed. This behavior suggests
formation of a self-similar, fractal agglomerate of the CB particles. In the
medium having a high affinity, the CB aggregates are well dispersed to no
agglomerates. These aggregates exhibit a slow relaxation process to their
diffusion. Thus, the structure and rheology of the CB particles/aggregates
changes with the affinity of the suspending medium. In this article, we report the
rheological properties of CB suspensions in three suspending media, a
polystyrene/dibutylphthalate solution (PS/DBP, low affinity), a rosin-modified
phenol-type varnish (Varnish-1, moderate affinity), and an alkyd resin-type
