School of Engineering and Materials Science
Research Student Awards
PhD Thesis: Innovative Bio-nanocomposites Based on Bacterial Cellulose
Author: GEA, Saharman
Supervisor(s): Ton Peijs
A variety natural materials that are environmentally friendly, renewable and low cost have been created. Bacterial cellulose (BC), which is produced by a harmless bacterium, Acetobacter xylinum, has been used as a reinforcement agent to form bio-nanocomposites. Apple and radish pulp which are themselves cellulosic, were blended with bacterial cellulose to produce a high quality nanopaper which can be used for special purposes. The resulting sheets are characterised in terms of their morphology as well as their mechanical and thermal properties. Another approach adopted was the combination of BC with bio-polymers such as poly (ε-caprolactone) and a commercially available starch based polymer, Mater-Bi. Freeze-dried BC, which was kept in its 3D shape, was used as a comparison. These innovative composite systems are non-petroleum based and are biodegradable. The morphology, structure, thermal properties and performance of the resulting bio-composites were investigated using scanning electron microscopy, fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, and by measuring the mechanical properties. Purification is a crucial step in removing impurities and another organic materials remaining in the BC. The BC gel which was purified in two steps, i.e. with 2.5 wt.% NaOH and then bleaching with 2.5 wt.% NaOCl respectively, showed a greater performance in its thermal and mechanical properties. In addition, it was shown that the cellulose I structure of BC is not converted to cellulose II. BC is an interesting material for in-vivo studies. However, to make it an interesting biological composite a suitable resin must be found. Poly (vinyl alcohol) (PVA) is a known water soluble polymer and is therefore a suitable candidate material. In this study BC was grown in a PVA solution to produce an in-situ composite. The concluding work for this project is an in-vitro study of BC for scaffolds for tissue engineering. The BC network was seeded with bovine chondrocytes (bone cells) obtained from an 18 months old deer and cultured into the BC gel to establish the viability of this material for medical applications.
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