THE RUB-FASTNESS OF NEEDLE-SHAPED IRON OXIDE PARTICLES

Abstract

The rub-fastness tests were carried out on needle-shaped iron oxide particles with different specific surface areas. Results were analyzed from kinetic viewpoint and compared with those obtained for spherical iron oxide particles. The removal process of needle-shaped particles by rubbing can be also treated as a reversible reaction of first order. The rate constant (k₁) of transfer of particles from adhered fabric to white cloth, the constant (k_-1) of the reverse process. of k₁, the equilibrium constant (K=k1/k_-1), and the removed amount (x/A) of particles by rubbing decreased with increasing particle size in a certain range, while those of spherical particles increased with increasing particle size. The rate constant k_-1 and the slopes of lines obtained from the plots of ln k₁ vs. 1/W, ln k_-1 vs. 1/W and ln K vs. 1/W, where W is the load weight, depend little on the particle size. These results were analogous to those obtained for spherical particles.