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Nanocellulose binders for fibre preforms: Creating the building blocks for high performance sustainable composites

Project Overview

Bacteral cellulose (BC) is produced by acetic acid producing bacteria, such as bacteria from the Acetobacter species. Comparing BC to NFC obtained through nanofibrillation of wood-based cellulose fibres (pulp), BC has the advantage of being free from wax, lignin, pectin and hemicellulose. It is highly crystalline in nature, with a degree of crystallinity of approximately 90%. BC inherently has nanometre dimensions and unlike plant-based sources of cellulose, does not require nanofibrillation. A single nanofibre of bacterial cellulose possesses a Young’s modulus of 114 GPa. In addition to this, BC is lightweight, non-toxic (it is actually part of a food product called nata-de-coco), renewable and biodegradable. It also has valuable intrinsic properties as a result of its small size that can influence the behaviour of the surrounding matrix due to its high surface area to volume ratio. The addition of nanocellulose to polymers provides improved mechanical and other physical properties. Sufficient evidence exists that BC (or nanocellulose) nanocomposites as well as green hierarchical composites with much improved properties can be made.

Randomly oriented non-woven natural fibre mats (also called fibre preforms) are produced by needle punching (essentially stitching) polymer fibres (typically a polyester) through loose compacted fibres. To make a composite, the fibre preforms are then placed in a mould and infused with a resin. More recently, polymer fibres are also commingled with natural fibres (typically flax, hemp or jute) or dispersed in a natural fibre suspension and vacuum filtered at high polymer volume fraction (50 vol.-%). This polymer fibre-natural fibre mat is then subsequently heated up to melt the polymer to produce a composite structure. The latter processes of producing composites are intrinsically scalable but they are limited by the choice of polymer fibres that can be used and, therefore, the type of matrices available to make composites. Moreover, making fibre mats using needle punching produces mats which lack sufficient strength for downstream handling. We have recently shown that natural fibres can be coated with nano-sized BC via two routes; (i) fermentation of BC in the presence of lignocellulose fibres or (ii) by dipping of lignocellulose fibres into a BC dispersion. The concept has also been extended to create randomly oriented short fibre preforms and its fibre reinforced (nano)composites utilising BC as the binder. This work will tackle the aforementioned shortcomings of the current state-of-the-art and offer new possibilities to natural fibre reinforced composite manufacturing.

Researcher

Dr. Koon-Yang Lee
Post-doctoral Research Associate

Supervisor: 
Prof. Alexander Bismarck

Sponsor:
EPSRC via KTS

 

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