Bacterial cellulose (BC) is an ultrapure form of cellulose nanofibres with mechanical performance exceeding that of E-glass fibres. The tensile stiffness and strength of a single BC nanofibre have been estimated to be up to 160 GPa and 6 GPa, respectively [1]. BC is produced as a continuous nanofibre network in the form of tough wet pellicle with high specific surface area. It is hypothesised that this continuous BC nanofibre network will serve as excellent nano-reinforcement for polymers with similar refractive indices, such as acrylic resin, for the production lightweight polymeric transparent armour with performance beyond the state-of-the-art. The introduction of such continuous nanofibre network into acrylic resin will introduce additional energy-absorbing mechanisms, including fibre de-bonding (due to an increase in fibre-polymer matrix interface), fibre re-orientation and fracture, enhancing the impact resistant of the resulting BC-reinforced acrylic resin without sacrificing optical transparency.<br/><br/>In this study, we report the tensile, fracture and impact properties of poly(methyl methacrylate) (PMMA) composites reinforced with bacterial cellulose (BC) pellicle. It was found that BC pellicle-reinforced PMMA composites with high optical clarity could be produced. By reinforcing PMMA with up to 5.0 wt.-% BC pellicle, a significant increase in tensile modulus compared to neat PMMA was observed. However, this improvement was accompanied by a significant decrease in tensile strength, strain-at-failure and impact strength due to matrix embrittlement. To circumvent this effect, 3 novel composite designs were developed: PMMA composites with uniformly dispersed BC throughout PMMA; sandwich structured construction consisting of BC pellicle-reinforced PMMA sandwiched between two neat PMMA sheets; hornified BC pellicle-reinforced PMMA composites. The tensile moduli of these composites were found to increase compared to neat PMMA. Furthermore, no significant detrimental effect in the tensile strength of the resulting composites was observed. This was attributed to the reinforcement architecture, which was designed to reduce BC nanofibre- PMMA interface such that the effect of matrix embrittlement was minimised. The best performing BC pellicle reinforced PMMA composites was reinforced with hornified BC pellicle, whereby the impact strength was 25% higher than neat PMMA, without sacrificing optical clarity.<br/><br/>

Optically transparent composites reinforced with cellulose nanofibers: Enhancing the fracture resistance and impact strength of acrylic with bacterial cellulose

2019 Spring National Meeting

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