Upgrading flax nonwovens: Nanocellulose as binder to produce rigid and robust flax fibre preforms

Published Date
Composites Part A: Applied Science and Manufacturing
April 2016, Vol.83:63–71, doi:10.1016/j.compositesa.2015.11.021
Special Issue on Biocomposites

• Author 

• Marta Fortea-Verdejo ^a
• Koon-Yang Lee ^b
• Tanja Zimmermann ^c
• Alexander Bismarck ^a,d,,

• aPolymer and Composite Engineering Group (PaCE), Institute for Materials Chemistry & Research, Faculty of Chemistry, Universität Wien, Währinger Straße 42, 1090 Wien, Austria
• bThe Composites Centre, Department of Aeronautics, Imperial College London, SW7 2AZ London, United Kingdom
• cApplied Wood Materials Laboratory, Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, CH-8600 Dübendorf, Switzerland
• dPolymer and Composite Engineering (PaCE) Group, Department of Chemical Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, United Kingdom

Available online 17 November 2015. 

Abstract

Typically in flax fibre nonwovens, the fibrous web is mechanically bonded (via entanglement and interlocking of fibres) or thermally bonded (by melting of polymer fibres). Recently, we showed that bacterial cellulose (BC) can be used as effective binder to produce rigid and robust natural fibre nonwovens without the need for polymer binders. Here, we further expand this work to manufacture flax nonwovens by utilising various types of (nano)cellulose, including nanofibrillated cellulose (NFC), BC and pulp fibres. Two preform manufacturing processes are investigated, namely single-step filtration and layer-by-layer filtration. Both BC and NFC serve as excellent binders for loose flax fibres due to their high surface area whilst pulp fibres are a poor binder for flax fibres. This is attributed to the low surface area of pulp compared to BC and NFC, which leads to a lower contact area between flax fibres and pulp. Furthermore, the larger fibre diameter of pulp results in a poorer packing efficiency and, therefore, a higher porosity of 67% compared to preforms made with BC or NFC as binder, which have a porosity of ∼60%. The manufactured preforms possess excellent tensile ( ,  ) and flexural (σ = 21.1 MPa, E = 2.2 GPa) properties. Layer-by-layer filtration process results in flax nonwovens, which exhibit even better tensile and flexural properties. This is hypothesised to be due to the better distribution of the fibrous nanocellulose network throughout the preform.

Keywords

A. Natural fibres

A. Biocomposite

A. Preform

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  Corresponding author at: Polymer and Composite Engineering Group (PaCE), Institute for Materials Chemistry & Research, Faculty of Chemistry, Universität Wien, Währinger Straße 42, 1090 Wien, Austria. Tel.: +43 (1) 4277 71301; fax: +43 (1) 4277 871302.

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