Abstract: In order to increase the accessibility of reagent's acting on wood powder in the modifying procedure,Morus alba wood flour was pretreated by planetary ball milling. The effects of dry and wet grinding methods as well as milling time on the particle size,crystallinity,and iodine adsorbance were investigated. The results showed that wood flour reached its minimum size after dry milling for 4 h,and the median diameter (D₅₀) was 8.982 μm. Moreover,the crystallinity of cellulose decreased obviously. Reunion phenomenon occurred when dry milling time was more than 4 h, so the particle size increased gradually. And the degree of crystallinity stayed unchanging with the increase of the milling time. The smaller the particle size of wood powder was,the higher the accessibility would be. Under the effects of the dispersion and inhibited reunion of water,the particle size gradually decreased with the increase of wet milling time. D₅₀ reached 4.357 μm when milling time was 12 h. In addition,the method of desiccation exerted tremendous influence on the accessibility of wet milling wood powder. The accessibility of sample by oven-drying was lower than that of the un-milling wood powder and reduced with the decrease of particle size. However,the accessibility of sample by freeze-drying increased significantly compared with un-milling wood powder and was higher than that of wood powder which was drying milling for the same time.

Key words: ball milling, Morus alba wood flour, reunion, accessibility