Fractal analysis of the influence of surface roughness of toner particles on their flow properties and adhesion behavior

In order to quantitatively evaluate the relationship between the minute roughness and powder behaviors such as macroscopic shear behavior and particle-particle interaction of toner particles with different particle surfaces, the FE-SEM image of a toner particle was processed in to a line image, and the particle outline image was analyzed using fractal dimension. In the fractal dimensional analyses, when the scaling was not less than or equal to 1/20 of the particle diameter, the fractal dimension was very large; it was inferred that the scaling was not suitable for showing a minute structure on the surface of the particle. In this study, the scaling was adjusted to less than or equal to 1/20 of the particle diameter. The relationship between the fractal dimension D and RMS surface roughness of the toner particle, which was determined by atomic force microscopy, had a weak first positive correlation. Subsequently, the influence of the surface coverage of SiO2 on the fractal dimension was examined. It was observed that the fractal dimension increased with the surface coverage of SiO2 in the condition of less than or equal to 26%. The relationships between the fractal dimension and the flow properties were examined using the rotary shear tester with conical rotor. When the mean particle diameter was almost constant, the fractal dimension was inversely proportional to the macroscopic shearing torque. Moreover, the relationships between the fractal dimension and the particle-particle interactions were examined using colloid probe AFM. It was observed that the fractal dimension was inversely proportional to the microscopic adhesion force. The relationship between the fractal dimension and the shearing force calculated by using torque was almost identical to that between the fractal dimension and the particle-particle interaction. (c) 2007 Elsevier B.V. All rights reserved.