4.4 A correlation between the optical property and the mechanical strength: from the CNF dispersion to the bio-based filament

Fossil fuel-based materials have long been utilized as the sources of filaments with their mechanical strengths strong enough to produce daily clothing to the composites of bulletproof vests. Not until recently, by taking advantage of the mechanical strength of the cellulose fibres itself, cellulose nanofibrils (CNFs) are proven to be an eco-friendly raw material for generating strong filaments that are comparable to or even surpass them. However, due to the inhomogeneity of the CNFs in the dispersion, a statistical number of filaments need to be tested after spinning to get the mechanical properties of the filaments. Therefore, this study aims to find a correlation between the CNF dispersion, spinnability, and the mechanical strength of the filaments. In this work, a flow-stop experiment using polarized optical microscopy (POM) will be used to study the optical properties of the flowing CNF dispersions. Then, the CNF dispersions will be spun into filaments and test the mechanical properties. The final goal of this study is to find a link between the CNF dispersion and the properties of the filaments to help decide whether or not it is an ideal dispersion to the final product.