Experiments and modeling of the viscoelastic behavior of polymeric gels

A polymeric gel is a cross-linked polymer network swollen with a solvent. Also, as is well known many polymeric materials exhibit viscoelastic behavior in their mechanical response. In this work, we report on our recent experimental observations and theoretical modeling involving the change in the viscoelastic response of the polymeric material VHB caused by equilibrium swelling in multiple solvents. To characterize this change, we have developed an experimental procedure that includes mechanical testing when virgin, free swelling, mechanical testing when swollen, and mechanical testing after drying. A model is used to help interpret the experimental results. The key finding of this work is that our results indicate that the viscoelastic behavior of initially dry VHB, reversibly, becomes essentially hyperelastic when swollen to equilibrium in multiple solvents.