(710f) Quantifying Sorption and Diffusion in Polymeric and Non-Polymeric Materials: Experimental Methods and High Fidelity Modeling

Quantifying the sorption and diffusion of vapors and gases in diverse types of materials is important to several industries and applications. Key parameters include the rate of diffusion, the sorption capacity, and the sorption mechanisms. Understanding these phenomena and capturing them in a model allow for predictions of material performance in realistic shapes and dimensions over the life of the system. Here we have developed a modeling and experimental capability to characterize and quantify sorption and diffusion of vapors and gases in materials. Our smallest scale experiments include dynamic vapor sorption and dynamic gas sorption as measured via gravimetric analysis of milligram to gram sized samples. By incrementally stepping up the vapor concentration or gas partial pressure we can monitor the sample mass uptake as a function of time to parametrize our dynamic sorption-diffusion model. Our initial experiments are performed with quasi-1-dimensional samples and the data is used to parameterize the models. Our physics based numerical model is a triple-mode sorption model that is coupled to a Fickian diffusion model; the three sorption modes are Henry’s absorption, Langmuir adsorption, and pooling. With this numerical model, one can then predict the sorption and diffusion in more complex, 3-dimensional parts to accurately model the behavior of real articles and systems. Validation experiments are key to building our confidence in our model both in 1D and 3D applications. By measuring 3D shaped samples in our gravimetric analysis instruments or via 3D outgassing experiments, the model can be validated. This model and accompanying experiments were developed to quantify and predict the vapor and gas sorption and outgassing (i.e. sinks and sources) of multiple materials in sealed systems, yet the experimental approach and physical based numerical model support a wide range of applications including adsorption and separation technology, materials designed as barrier materials (e.g. polymeric protection layer on photovoltaic cells), and predictions of material outgassing in sealed systems over long durations (e.g. space and satellites, weapon systems, etc). Here we will discuss our sorption-diffusion numerical model and the accompanying 1D and 3D experiments and simulations on several materials including polymers and non-polymeric samples (e.g. Sylgard-184, Zircar RS-1200 i.e. an alumina ceramic composite, etc).

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