EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Bacterial cellulose (BC) is an ultrapure form of cellulose nanofibres with mechanical properties exceeding those of both Kevlar and E-glass fibres. A single BC nanofibre has an estimated Young’s modulus of 160 GPa, which makes it a promising reinforcement for biocomposites. In this work, the focus lies on reinforcing impact modified (IM) acrylic to increase its impact strength while maintaining high transparency. The aim is to create a more lightweight alternative to glass-based composites, which are currently used in impact-resistant, protective applications like windshields or bulletproof casings. The challenge here is to obtain a highly transparent composite while using BC nanopaper which is opaque in its untreated form.
In this study composites with alternating sheets of IM-acrylic and layers of BC nanopaper were prepared, using one, three and five layers of nanopaper. The dried BC nanopapers were vacuum impregnated with a ductile, UV-curable matrix, sandwiched in between plates of IM-acrylic and polymerized. As a reference, samples without the BC were prepared by sandwiching plates of the IM-acrylic with the UV curable matrix. All samples with BC showed high transparency with a transmittance of up to 84 % at 550 nm compared to 90 % of pure IM-acrylic at a sample thickness of 3 mm. The impact strength, measured by the Charpy impact test, was increased by 48 % upon the use of one layer of BC and by 130 % to 26.7 KJ/m2 when using five layers of cellulose compared to the neat IM-acrylic. The reference samples exhibit a 2 – 10 % higher transmittance compared to the corresponding samples with BC, however, their impact strength is around 50 % lower, respectively. This study shows that using BC as reinforcement in IM-acrylic based composites results in increased impact properties at a minimal loss of transparency.