Preparation of biodegradable recycled fiber composite film using lignin-based polyurethane emulsion as strength agent

Poor wet mechanical and barrier properties restrict cellulose-based materials from replacing petroleum-based plastics. Herein, an environmentally benign blocked lignin-based water-borne polyurethane emulsion which could be stored stably was prepared for the development of a hydrophobic, translucent, and biodegradable recycled fiber composite film through a blocked terminal isocyanate group. The tensile strength, Young's modulus, and toughness of the film were determined to be 48.15 MPa, 4.66 GPa, and 755.93 kJ m- 3, respec-tively, which were 2.7, 3.9, and 4.3 times higher than of control. Besides, the composite film showed excellent water stability with improved water contact angle (114 degrees) and wet strength (30.60 MPa) compared to the control. Furthermore, the composite film manifested excellent UV-blocking properties and it had good thermal stability. The developed functionally integrated composite film with exceptional physiochemical properties is expected to be applied as a green packaging and construction material.