Influences of Coagulation Conditions on the Structure and Properties of Regenerated Cellulose Filaments via Wet-Spinning in LiOH/Urea Solvent

Dissolving cellulose rapidly at low temperature by using solvents (NaOH/urea, NaOH/thiourea, LiOH/urea or NaOH/thiourea/urea) opens a new chapter for the preparation of high-performance cellulose filaments for the unique structure containing nanofibers. In our previous work, it was found that the coagulation rate is a key to construct the nanofiber structure and thus to achieve high performance of regenerated cellulose filament (RCF) via wet-spinning. In this work, phytic acid salt was used to further adjust the coagulation rate for a better control of the structure of RCF. It was found that adding a small amount of salt would promote a rapid diffusion of phytic acid from the skin to the core of cellulose filament, resulting in a relatively compacted structure accompanying an increasing skin yet decreasing core. However, excessive salt would result in a decrease of neutralization capability of phytic acid, leading to a less compacted structure in the filament. The optimum salt concentration was found to be 5% at which phytic acid could permeate to the center of the filament and maintain good neutralization capability. The best tenacity of the filaments achieved is about 3.43 cN/dtex, which preponderates over that of commercial viscose rayon. A comparison study between commercial viscose rayon and the obtained filament was carried out to further demonstrate the importance of nanofibers for the enhancement of cellulose filaments. In this work, we systematically investigated the influence of phytic acid salt concentration on the structure and properties of novel regenerated cellulose filaments, which provides a positive guidance on the environmentally friendly cellulose industrialization.