Irradiation by a 365nm beam onto CaCO3 powder under comminution was carried out for the surface modification of a powder with a photosensitive acrylic oligomer. A commercial impact mill (New Cosmomizer I, Nara Machinery) was modified by providing UV transparent windows on the self-recycling path. The coated fine particles were washed with acetone to remove non-cured oligomer and were then subjected to thermal analyses, TG-DTA. The weight loss increased linearly with the DTA peak area due to thermal decomposition of the surface polymer. The decomposition temperature of the surface polymer was elevated by the irradiation, indicating stabilization of the surface polymer. The existence of the stable surface film was verified from the flocculation behavior of the modified particles in water, the larger apparent particle size, and the decrease in the dissolution rate of CaCO3 into a diluted aqueous solution of HCl.
