Fibrillation of dried chitin into 10–20 nm nanofibers by a simple grinding method under acidic conditions

Chitin nanofibers were prepared from dried chitin by fibrillation using a grinding apparatus. The fibrillated chitin samples were observed by FE-SEM and were found to have a fine nanofiber network; the structure was highly uniform with a width of 10–20 nm and a high aspect ratio. Mechanical treatment under acidic conditions is the key to fibrillating dry chitin. The cationization of amino groups on the chitin fiber facilitates fibrillation into nanofibers by electrostatic repulsions. Even though the degree of substitution of amino groups was only 3.9%, it was enough to break the strong hydrogen bonds between the nanofibers. Furthermore, optically transparent nanocomposites using chitin nanofibers with acrylic resin were prepared to examine the fibrillation properties of dry chitin and nanofiber homogeneity. Since dried chitin was fully fibrillated, the optical losses of these composites were less than 2% even after the drying process. Moreover the films were characterized by X-ray diffraction, and TGA.