(435c) Modeling and Uncertainty Quantification of Vapor Diffusion and Reactions in Polymer

Yunwei Sun, Hom Sharma, and Elizabeth Glascoe

Lawrence Livermore National Laboratory

April 14, 2017

Characterizing the reactive transport of vapor through porous materials is important in predicting the aging and compatibility of polymers that are often used to repel moisture and protect more sensitive materials within. For example, water intrusion into an electronic device (e.g., photovoltaic cells) through a polymer layer may result in corrosion, shorting, and other types of electronic failure. A variety of mathematical models, together with statistical methods and computer algorithms, have been developed to understand and quantify vapor diffusion and sorption in polymers. However, most of those models are limited to steady-state diffusion and equilibrium sorptions and fail to address the dynamic behavior that is directly associated with material aging and compatibility. In this study, we develop a high-fidelity diffusion model coupled with triple-mode sorptions with joint and iterative experimental and modeling capability to characterize and quantify vapor sorption and diffusion through polymeric materials.

When Langmuir adsorption is treated as a kinetic reaction, the corresponding ordinary differential equations (ODEs) are usually solved using ODE solvers. The computational expense for solving those ODEs of the dynamic adsorption has limited the applicability of the high-fidelity model. To accelerate the simulation of coupled diffusion and sorption processes, we developed a statistical approximation method using computationally cheap surrogate models (e.g., algebraic polynomials) that replace the ODE solutions of adsorption and are coupled with the diffusion equations. Since the polynomial presentation of the adsorption term is obtained in a standard format prior to modeling coupled sorption-diffusion, the adsorption operator can be expressed as input data in the transport code. Compared to conventional operator-splitting methods, the polynomial approximation of adsorption offers better computational efficiency. The methodology is demonstrated and validated using a dynamic Langmuir adsorption model that is coupled to diffusion and absorption models and applied to a water vapor sorption-diffusion process in polydimethylsiloxane polymers.

To avoid over parameterizing the physical model, we are conducting global sensitivity analysis to establish a cost-effective model form and identify the most sensitive parameters in the model. Using the developed model, we quantify uncertainty propagation from uncertain parameters to material performance measures.

This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.