The effect of cellulose molecular weight on internal structure and properties of regenerated cellulose fibers as spun from the alkali/urea aqueous system

The low-temperature alkali/urea aqueous system has received wide public attention since it is a better method to reduce pollution by preparing the regenerated cellulose fiber through the green dissolution system. Since molecular weight has a significant impact on the solubility and mechanical property of regenerated cellulose fiber; thus, we designed this experiment that cellulose materials with molecular weight ranging between 6.8 x 10(4) to 13.5 x 10(4) were employed for wet-spinning in alkali/urea aqueous system. It is found that as molecular weight of cellulose increases, cellulose solution decreases in solubility but cellulose molecular chain aggregates increase. However, bath the stability and viscosity of cellulose solutions almost remain unchanged with the change of molecular weight. As for the spun fibers, it is found that the orientation and crystallinity are relatively high when the molecular weight is low (6.8 x 10(4) -9 x 10(4)). These are excellent mechanical properties However, unlike conventional polymers, when molecular weight further increases to 9 x 10(4) -13.5 x 10(4) , the degree of orientation and crystallinity gradually decreases. This is due to a large number of entanglements between adjacent molecular chains, thereby hindering the molecular chain orientation along with reduced mechanical property. Our work demonstrates that the considerable molecular weight of cellulose is neither good for dissolution nor spun fibers' mechanical property. The choice of cellulose with relatively low molecular weight is essential not only for the excellent dissolution but also for fiber property.

Automated summary

The study reveals that the molecular weight of cellulose affects solubility, orientation, and mechanical properties of the fibers. When the molecular weight of cellulose is low, the fibers exhibit high orientation and crystallinity, leading to excellent mechanical properties. However, as the molecular weight increases, solubility decreases while the orientation and crystallinity reduce, ultimately affecting mechanical properties.