Preparation by combined enzymatic and mechanical treatment and characterization of nanofibrillated cotton fibers

The effects of cellulases and their combination with mechanical fibrillation for nanofibrillation of cotton boll and dried cotton fibers and their subsequent application were investigated. The prepared nanofibrillated fibers were analyzed and compared in terms of morphology and solid-state properties. It was found that Trichoderma reesei cellulase, mainly consisting of cellobiohydrolases, was relatively suitable for nanofibrillation of cotton boll fibers. Nanofibrillation of cotton fibers, especially when previously dried, proved difficult without cellulases. Our results suggest that dried cotton fibers have strong hydrogen bonds, as in hornification during drying of wood pulp. However, we could nanofibrillate not only never-dried fibers of cotton boll but also dried cotton to 10-50 nm in width by treatment with cellulase mainly consisting of cellobiohydrolase, although a few bundles of around 100 nm remained. These results indicate that cellulase treatment cut and swelled the dried cotton fibers by breaking the strong hydrogen bonds, enabling their nanofibrillation. Nanofibrillated cotton fibers prepared using cellulases also contained relatively pure cellulose with greater crystallinity and higher thermal degradation temperatures compared with other cellulose nanofibers. Considering these characteristics, such cotton fibers nanofibrillated using cellulase would be applicable in medical and composite industries.