Polymeric materials consist of long chain of molecules, which form a polymer network. Due to the interactions between polymer chains, many polymeric materials are known to exhibit viscoelastic behavior.  When a polymer network is exposed to a suitable solvent, the solvent molecules are able to diffuse inside the network, causing it to undergo a volumetric deformation, known as swelling.  A polymeric material in this mixed and swollen state is known as a polymeric gel.  Polymeric gels are ubiquitous, they are found in a wide variety applications including: soft robots; packers in the oil industry; valves in microfluidic channels; and a diverse array of biomedical applications. In addition, many biological tissues are gel-like in constitution, which makes a thorough mechanistic understanding of these materials essential for our understanding of mechanical response of human, animal, and plant tissues.

Although many novel applications for gels have been demonstrated in the literature, actual use of devices utilizing these materials is still quite limited. One of the major reasons for this state of affairs is that a widely agreed upon multiphysics constitutive theory and an attendant numerical implementation for simulation-based design using these materials does  
not exist.  Recent years have seen the development of a vast number of models aimed to capture the coupled diffusion-deformation behavior of polymeric gels.  However, there is an insufficient amount of experimental data to complement such theoretical research. Accordingly, there is a gap between existing models and our emergent experimental research, indicating that nearly all current models are in need of significant improvement.

  
The objective of our research is to experimentally determine the change in behavior of viscoelastic polymers between the dry and swollen states.  The experimental procedure includes free swelling experiments along with large deformation mechanical testing in both dry and swollen states.  We employ commercially available VHB 4910, a polymeric material known to exhibit viscoelastic behavior in dry state, and which is well known to swell when exposed to n-Pentance, o-Xylene, and Toluene.  Our experimental program allows us to observe key features of the viscoelastic response of the material, and make an improved model.  

Our newly developed experimental program provides transformational insight into the behavior of swollen viscoelastic polymers and helps to bridge the gap between experimental and theoretical research.   Our model is successfully calibrated against the obtained experimental data, thus proving capable to replicate the major features of viscoelastic gel behavior observed in our experiments. The calibration of our constitutive model showed (i) low utilization of the time-dependent stress contribution for the samples fully swollen in n-Pentane; (ii) almost complete absence of the time-dependent stress contribution for samples fully swollen with o-Xylene and Toluene.


Experiments and Modeling the Viscoelastic Behavior of Polymeric Gels

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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