This thesis describes the fabrication of novel green materials using nanocellulose as
the building block. Bacterial cellulose (BC) was used as the nanocellulose
predominantly in this work. BC is highly crystalline pure cellulose with an inherent
fibre diameter in the nano-scale. A single BC nanofibre was found to possess a
Young’s modulus of 114 GPa. All these properties are highly favourable for using
BC as a nanofiller/reinforcement in green nanocomposite materials.
In this work, the surface of BC was rendered hydrophobic by grafting organic acids
with various aliphatic chain lengths. These surface-modified BC was used as nanofiller
for poly(L-lactide) (PLLA). Direct wetting measurements showed that the BC
nanofibre-PLLA interface was improved due to the hydrophobisation of BC with
organic acids. This led to the production of BC reinforced PLLA nanocomposites
with improved tensile properties. Nanocellulose can also be obtained by grinding of
wood pulp, producing nanofibrillated cellulose (NFC). The surface and bulk
properties of one type of NFC and BC were compared in this work. Furthermore, the
reinforcing ability of NFC and BC was also studied and it was observed that there is
no significant difference in the mechanical performance of NFC or BC reinforced
nanocomposites.
A novel method based on slurry dipping to coat sisal fibres with BC was developed
to modify the surface of natural fibres. This method can produce either (i) a densely
BC coating layer or (ii) “hairy” BC coated sisal fibres. Randomly oriented short BC
coated sisal fibre reinforced hierarchical composites were manufactured. It was
found that hierarchical (nano)composites containing BC coated sisal fibres and BC
dispersed in the matrix were required to produce composites with improved
mechanical properties. This slurry dipping method was also extended to produce
robust short sisal fibre preforms. By infusing this preform with a bio-based
thermosetting resin followed by curing, green composites with significantly
improved mechanical properties were produced. BC was also used as stabiliser and
nano-filler for the production of macroporous polymers made by frothing of
acrylated epoxidised soybean oil followed by microwave curing.