Substantial size reduction of banana fibres and enhancement of fibre properties achieved through a single mechanical treatment

This study aims to encourage the large scale production of micro-cellulose fibres (MCF), especially in developing economies. Micro-fibres have been extracted from banana pseudo-stem agro-wastes to valorise the latter. The particularity of this study is that a commercial food wet grinder, an equipment necessitating less investment cost as compared to the traditional supermass colloider (SMC) machine, has been employed to yield micro-fibres. For enabling maximum controllability of the process, the effect of two grinding parameters (the gap distance and the number of passes) were investigated. The results revealed the viability of such a mechanical equipment: from SEM results, 95% reduction in fibre diameter (comparable to the 99% size reduction for the SMC machine) and from XRD results, high percentage crystallinity (76–80% corresponding to an increase of 25–30%) were obtained. The optimal conditions resulting in these conditions were: smallest possible gap distance (800 µm) and highest number of passes (30). Another singularity of this study is that the gap distance proved to be more important than the number of passes in terms of the fibre diameter reduction, lignin and hemicellulose reduction, crystallinity and fibrillation. Lignin and hemicellulose, despite having been decreased to 13% and 7–9% respectively during the process, have been observed to enhance fibrillation. Thus, a high degree of fibrillation (yielding micro-fibres of diameter 1–2 µm) was obtained at a relatively low power consumption (4.1 kWh/kg fibre). Finally, a detailed explanatory mechanism based on the literature-reported viscoelasticity of lignin has been given to explain how it facilitates fibrillation.