Milling in Seconds Accelerates Acetylation of Cellulose in Hours.

A new sustainable synthetic method for cellulose acetate was developed by a combination of I2-catalyzed solid-liquid acetylation of cellulose and a milling process reducing the crystallinity of cellulose within a few seconds. Milled low-crystalline cellulose was acetylated faster than the original cellulose with higher crystallinity. The plausible factors of acceleration were the conversion of the hydroxy group in hydrogen bonds into reactive ones and the efficient formation of the catalytic species I+ by the enhanced formation of I3 - assisted by the amorphous domain of the milled cellulose, while the morphological and structural changes were ignorable.

Novel method for producing amorphous cellulose only by milling.

The present study investigated a novel method for producing amorphous cellulose by milling without adding water. A new type of milling machine was developed (called a shear and cooling milling machine (SCMM)), which was capable of applying mechanical shear and cooling during the milling process. The SCMM consisted of a pair of mortars attached to a servomotor and a ring cooler. Wide-angle X-ray diffraction (WAXD) analysis was used to determine the cellulose crystallinity in samples produced using the SCMM at different milling temperatures. The results of WAXD for cellulose powder milled at lower temperatures exhibited no diffraction peaks. This experimental result demonstrates that the SCMM produces amorphous cellulose easily by cooled milling without the addition of water. The milling conditions, such as the applied shear and cooling, can be used to control the crystallinity of cellulose.