High-performance green nanocomposites using aligned bacterial cellulose and soy protein

Maximum potential of any fibers as reinforcing agent in composite materials can be obtained through their preferential alignment. In this study, a facile method has been developed to fabricate high-performance green composites based on aligned bacterial cellulose (BC) as reinforcing agent and soy protein as bio-resin. Aligned BC nanofibrils were produced by cultivating it inside polydimethylsiloxane (PDMS) tubes followed by an optimum wet-stretching. The curved geometry of the inner tube surface provided the bacteria a preferred direction for growth. Further improvement in alignment was obtained with optimized stretching of the tube-shaped BC (TBC) at a crosshead speed of 0.03 mm/min and draw ratio of 1.20. Stretched TBC showed superior mechanical properties in comparison to the conventionally grown BC pellicle. Stretched TBC resulted in higher tensile strength (230% increase), modulus (330% increase), and orientation indices (135% increase) compared to the conventional BC pellicle. Soy protein isolate (SPI)-based fully green composites reinforced with TBC were prepared by a vacuum-assisted resin impregnation process, and the same stretching method was applied to the TBC-SPI gel. The stretched and cured composites showed significant improvements in the tensile strength (from 40 MPa to 150 MPa) and modulus (from 2 GPa to 8 GPa) in comparison to the conventional BC reinforced composite because of the enhanced alignment of BC nanofibrils. (C) 2017 Elsevier Ltd. All rights reserved.