Characterization of highly accessible cellulose microfibers generated by wet stirred media milling

In this work, highly accessible cellulose microfibers produced from kraft wood pulp by a novel method based on a single mechanical treatment with a wet stirred media mill were characterized. The high mechanical stress of milling resulted in the complete disintegration of the fiber cell wall and produced cellulose microfibers with a length of below 50 μm and diameter ranging from a few hundred nanometers to 1 μm after only 5 min of milling. The noticeable increase in BET (Brunauer, Emmett, Teller-method) surface area from the initial value of 2.2 m2/g to 25–60 m2/g and decrease in crystallinity index from 65% to 20–30% during milling (5–60 min) indicated that microfibers possessed a highly accessible surface area and a large number of amorphous sites. This was also supported by the significantly increased reactivity of the microfibers compared to the reference pulp in the periodate oxidation reaction of cellulose to dialdehyde cellulose.