Edinburgh Napier University

  The thesis describes a programme of work to develop a novel cellulose based fibre. The most important innovative step in this work lies in the manufacture of the fibre from a chiral nematic suspension of plant based cellulose nano-fibrils. In the course of the project a number of key steps have been addressed in the development process. These included:
• Developing a method for extraction of nano-fibrils from wood and cotton based pulp and filter paper;
• Development of concentrated chiral nematic suspensions of the nano-fibrils suitable for extrusion (spinning);
• Spinning a continuous fibre or filament;
• Fibre characterization.

A key objective of the work was to understand the factors that could contribute to nematic order of the nano-fibrils in the fibre and produce a high strength fibre.

The fibres developed showed reasonably good strength potential and good stiffness properties with the best fibres having a tenacity of between 40 and 100 cN/tex and an initial modulus of 5000-6000 cN/tex. These values fall midway between lyocell and Kevlar. Two patents have to date been published based upon the developments described in this work (Turner et al., 2010, 2011). However, the work highlighted a number of gaps in current knowledge that prevented development of the full potential strength properties of these fibres. These included:
• Incomplete knowledge of the gel conditions required to achieve complete alignment of the fibrils in the spinning process;
• Challenges in being able to draw the fibre sufficiently during spinning to produce target fibre diameters of 5-10μm;
• The linear density of the spun fibres had a key impact on fibre strength. It was only when linear density values dropped below 1 tex (1g/km) that a significant increase in fibre strength occurred. Factors that had an important impact on linear density included solids content of the suspension, zeta potential, extrusion rate and fibre drying temperature. All these factors relate directly to the mobility of the cellulose nano-fibrils and their subsequent ability to align under flow during spinning.

The thesis can be seen as a first phase in an ongoing process to develop a new approach to the manufacture of cellulose based industrial textile fibres.