The reinforcement effect of cellulose nanofiber on Young's modulus of polyvinyl alcohol gel produced through the freeze/thaw method

Cellulose nanofiber (CNF) is the most effective reinforcement fiber for enhancing the physical properties of water-soluble polymers. Here, effect of CNF on the Young's modulus of a polyvinyl alcohol (PVA) hydrogel produced through the freeze/thaw method is examined. PVA/CNF composite gels with different contents of CNF and PVA were produced without significant aggregation of CNFs during the freeze/thaw process. The Young's modulus of the produced PVA/CNF gel gradually increased as the CNF content increased, and it was confirmed that CNF had a marked reinforcement effect. In gel with PVA = 7 vol%, percolation networks formed at CNF >= 0.6 vol%. Furthermore, adding ca. CNF = 1.5 vol% resulted in a 250% increase in the gel's Young's modulus. In addition, mechanical interaction was observed between the PVA and CNF networks. It was suggested that, similarly to CNF networks, PVA networks also limit the deformation of CNF networks.