| Natural cellulose fibres are gaining acceptance as glass fibres replacements in composite manufacturing. Currently only long fibres from plants such as hemp, flax, sisal, jute etc. are used. However within the cell walls of all plant cells, there is a second level of fibre structure on a very small scale. These are bundles of cellulose nanofibres with a diameter range between 5 to 50 nm and lengths of thousands of nanometres. Theoretically these nanofibres can have stiffness up to 130 GPa and strength up to 7 GPa.;In the present work, a novel technique was developed to extract cellulose nanofibres from long fibres using a combination of chemical and mechanical treatments. Their structure was investigated by atomic force microscopy and transmission electron microscopy. Selective chemical treatments increased cellulose content to 94% from 73%. The calculated aspect ratio (length/diameter) of the nanofibres was approximately 75. Estimated crystallinity of the cellulose nanofibres was more than 55%. Reinforced composites films comprised of 90% polyvinyl alcohol and 10% nanofibres were also prepared. Nanofibres reinforced films demonstrated at least 4--5-fold increase in Young's modulus, as compared to the pure PVA film. |
