Effects of Hydration on the Mechanical Response of a PVA Hydrogel

Abstract

The effect of drying on the tensile behavior of a dual cross-linked poly(vinyl alcohol) (PVA) hydrogel is studied here. This gel contains about 90% water when fully hydrated. The mass–volume relationship of the gel is measured using a microbalance with a density kit. Our results show that as the gel dries the volume is linearly proportional to the mass. The impact of drying on the gel’s mechanical properties is measured in uniaxial tension tests, which include loading-unloading tests at three different constant stretch rates, a complex loading history test and a stress-relaxation test. Data from specimens with different hydration levels can be described by a constitutive model of the gel. The results show that the model parameters are strongly dependent on hydration level and that as the gels dry, the gels are much stiffer than those in the fully hydrated state.Key wordsViscoelasticityHydrationLarge strainDual cross-linked hydrogel