Melt processing of cellulosic fibres with only water as plasticiser

Emile Engel

Upon heating, native cellulose fibres degrade before softening or melting. This is a well-known limitation to the development of cellulosic thermoplastics as a sustainable alternative to fossil fuel-derived polymers.

Here, conventional cellulose pulp fibres (beaten kraft) were partially chemically modified to impart exceptional ductility (strain-at-break of approximately 30%) and thermoplastic characteristics, while preserving their morphology as fibres. Melt processing of these modified fibres is demonstrated, by twin-screw extrusion, using only water as plasticiser. Fibres at 47% degree of modification were melt processed at a controlled moisture content of either 25 or 63 wt% and at a processing temperature of either 70 or 100 °C. Extruded materials were characterised by SEM, XRD analysis, thermal analysis and tensile testing. Although shearing, during twin-screw extrusion, damages the fibres, resulting in moderate losses in tensile strength and elasticity, the exceptional ductility of the material is preserved and may even be enhanced by the processing.