The effects of boric acid on the rheological behavior of time dependent structure formation in PVA/DMSO solutions

Lots of studies have been carried out to improve the strength of polyvinyl alcohol (PVA) fibers. One of these studies is crosslinking spinning for a good quality fiber. As a crosslinking agent, boric acid (BA, H₃BO₃) was used. PVA can crosslink with BA without adding cation in using dimethyl sulfoxide (DMSO). The effects of BA addition and molecular weight (MW) on the formation of the physical structure in PVA/DMSO solutions were investigated. The results showed that the time dependence of the rheological responses was greatly influenced by the BA addition to the PVA/DMSO solutions. The results also showed that the BA addition to the PVA/DMSO solutions increased the dynamic viscosity (η′), the storage modulus (G′), and the loss modulus (G″) of the PVA/DMSO solutions. Increasing MW of PVA also decreased the time dependence. In addition, the BA addition to the PVA/DMSO solutions decreased the gelation time of the PVA/DMSO solutions. These overall results suggested that the structure formation through specific interactions between PVA molecules and BA resulted in the time dependent changes of the rheological properties of the PVA/DMSO solutions.