Silica-rich regenerated cellulose fibers enabled by delayed dissolution of silica nanoparticles in strong alkali using zinc oxide

Silica nanoparticles (SNPs) dissolve in alkaline media, which limits their use in certain applications. Here, we report a delayed dissolution of SNPs in strong alkali induced by zinc oxide (ZnO), an additive which also limits gelation of alkaline cellulose solutions. This allows incorporating high solid content of silica (30 wt%) in cellulose solutions with retention of their predominant viscous behavior long enough (ca. 180 min) to enable fiber wet spinning. We show that without addition of ZnO, silica dissolves completely, resulting in strong gelation of cellulose solutions that become unsuitable for wet spinning. With an increase of silica concentration, gelation of the solutions occurs faster. Employing ZnO, silica-rich regenerated cellulose fibers were successfully spun, possessing uniform cross sections and smooth surface structure without defects. These findings are useful in advancing the development of functional man-made cellulose fibers with incorporated silica, e.g., fibers with flame retardant or self-cleaning properties.

Automated summary

The study found that adding zinc oxide (ZnO) in strong alkali can delay the dissolution of silica nanoparticles (SNPs), allowing cellulose solutions containing silica to maintain viscous behavior during wet spinning. With ZnO added, silica-rich regenerated cellulose fibers with uniform cross sections and smooth surface structure can be successfully spun.