Development of a superhydrophobic cellulose fabric via enzyme treatment and surface hydrophobization

Enzymatic hydrolysis is a common finishing method for cellulosic materials, to improve fabric softness, appearance, and surface properties. However, its potential to trigger superhydrophobicity has not been studied in depth. In this study, a superhydrophobic cellulose fabric was fabricated in two steps. Micro-/nano-hierarchical roughness on the fabric surface was achieved by cellulase from Aspergillus niger, through enzymatic hydrolysis. Subsequently, hydrophobization was carried out by a dip coating method, using polydimethylsiloxane (PDMS). Enzyme concentration and treatment temperature were varied to find the values that provided the greatest superhydrophobicity. As enzyme concentration and temperature increased, the nano-scale roughness increased, along with weight reduction. The degree of crystallinity and reduction in tensile strength were also increased with weight loss via enzyme hydrolysis. As air pockets were formed by micro-/nano-structures on the fiber surface, the water contact angle increased and the shedding angle tended to decrease. The sample treated with 5 g/l enzyme at 60 ℃ for 60 min and coated with PDMS 1 wt.% coating solution had the greatest superhydrophobicity, with a water contact angle of 162° and a shedding angle of 7.0°. The weight loss and reduction in tensile strength of the developed superhydrophobic fabrics were 2.9% and 39.0%, respectively. This approach reduces the necessity for an additional process to introduce nano-scale roughness, and it has the potential to produce superhydrophobic cellulosic biomass for outdoor clothing.