The effect of particle size of hydrated ferric oxide on the rubbing fastness.

The effect of particle size on the rub-fastness has been investigated from the kinetic viewpoint. Hydrated ferric oxide was used as the model of dye because it was rather easy to prepare the several required particle sizes.The removal amount of hydrated ferric oxide by rubbing increases with increasing particle size and its removal process can be treated as a reversible reaction of first order. The rate constant of transfer of hydrated ferric oxide from adhered fabric to white cloth (k1), the rate constant of reverse process (k-1), and equilibrium constant (K=k1/k-1) increase with increasing particle size (D) and are proportional to D0.74, D0.13 and D0.61, respectively.