Hydrophobic cellulose films with excellent strength and toughness via ball milling activated acylation of microfibrillated cellulose

• Exfoliation and acylation of microfibrillated cellulose (MFC) was realized.
• Modified MFC films showed largely enhanced tensile strength and toughness.
• Excellent water resistance and water vapor permeability were achieved.
• Optical performance of the modified films was also improved.
• We provide an efficient and easily industrialized method for MFC modification.

Cellulose films with excellent mechanical strength are of interest to many researchers, but unfortunately they often lack the ductility and water resistance. This work demonstrates an efficient and easily industrialized method for hydrophobic cellulose films made of modified microfibrillated cellulose (MFC). Prior to film fabrication, the simultaneous exfoliation and acylation of MFC was achieved through the synergetic effect of mechanical and chemical actions generated from ball milling in the presence of hexanoyl chloride. Largely enhanced tensile strength and elongation at break have been achieved (4.98 MPa, 4.37% for original MFC films, 140 MPa, 21.3% for modified ones). Due to hydrophobicity and compact structure, modified films show excellent water resistance and decreased water vapor permeability. Moreover, optical performance of modified films is also improved compared with the original MFC films. Our work can largely expand the application of this biodegradable resource and ultimately reduce the need for petroleum-based plastics.