Gelation time characterization method for polyvinyl alcohol-based hydrogel

Introduction: Hydrogel and its gelation time have received great interest from material researchers and engineers. In this study, the method to evaluate the gelation time for hydrogel material was proposed. Methods: The gelation test was conducted based on DV2T Brookfield viscometer and the newly designed gel timer (GT-2000). The method was applied to polyvinyl alcohol (PVA) solution with glutaraldehyde (GA) as a crosslinker. The blended hydrogel, including PVA and hydroxypropyl cellulose (HPC) was also prepared to confirm the versatility of the proposed method. The water uptake was conducted to confirm the relationship with the gelation time. Results: With 3 wt% polymer solutions, both starting (torque is larger than 1%) and ending time (torque is larger than 90%) of the gelation could be detected. On the other hand, only the starting of gelation process could be measured with 1.5 wt% of the similar solution. When GA or the polymer concentration decreased, the gelation time could be reduced. By adding HPC to the PVA solution, the gelation time was reduced. The gelation time and water uptake were correlated with PVA hydrogel, while this type of relationship could not be detected in the PVA-HPC hydrogel samples. The addition of 1 wt% of HPC significantly improved the value of water uptake (more than 50 times). Conclusions: In conclusion, the proposed gelation time method could be successfully applied to the PVA-based hydrogel and performed as a preliminary characterization technique for hydrogel materials.