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, respectively, 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°) 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.