磁性粉塗料のレオロジー的挙動について

抄録

Some rheological behaviors of paints containing magnetic powders (γ-Fe₂O₃) were investigated from the view point of interfacial phenomena, compared with the paints containing non-magnetic powder (α-Fe₂O₃), and the following results were obtained:
Both α-and γ-Fe₂O₃ paints without dispersing agent, show the structural viscosity, and its tendency is more remarkable in the former paint.
By the addition of the dispersing agents, the structure forming action of particles in α-Fe₂O₃ paints is weakened and its flow character is altered to a Newtonian pattern. On the other hand, in the γ-Fe₂O₃ paints, the structure still remains and Bingham-type flow is maintained.
These behaviors were considered to be caused by the formation of different structures in each paints. In the α-Fe₂O₃ paints, the particles form three-dimensional honey-comb structures as shown in Fig. 10 (b), only with the interparticular attractive forces. In the case of the γ-Fe₂O₃ paints, particles were arranged as chains or closed chains shown in Fig. 10 (a), by magnetic attractive force.
The applicability of Casson's equation, the appearence of 2nd Newtonian region and the thixotropic behaviors for the γ-Fe₂O₃ paints will mean the degradation of the chain to smaller units by shearing force, together with the rearrangement and orientation.