Sorption and diffusion in polymeric materials is of great interest in wide range of applications .To many application, moisture sorption and diffusion can be catastrophic due to the change in chemical and mechanical properties of materials over time. The uptake and outgassing of moisture is also associated with aging and compatibility issues in a system, which can directly alter the lifetimes and viability of system assemblies and screening new materials for future designs. The process is dynamic and consists of different sorption modes and varies dramatically in different materials. Therefore, a detailed understating of the moisture uptake and diffusion is crucial.<br/>In this study, we investigate the moisture sorption and diffusion phenomena using a combined experimental and modeling approach. Polymeric materials (for example: KaptonH and Kapton HN) are investigated over a wide range of temperatures and relative humidities (RH) to quantify the moisture transport mechanism as shown in the figure 1 below. Gravimetric type dynamic vapor sorption (DVS) experiments were employed to measure the moisture uptake and used for the modeling. A reactive transport model is used which includes a triple-mode sorption model that includes absorption, adsorption, and pooling of species, molecular diffusion, and chemical reaction kinetics. Our sorption experiments and modeling results quantify the differences between the two example materials and demonstrate a substantially larger adsorption capacity and moisture affinity for Kapton HN compared with Kapton H. A distinct pooling mode can be seen above 70% RH in both materials, however the pooling mode is larger in Kapton HN. Density functional theory calculations are performed to investigate the impacts on moisture uptake due to CaHPO<sub>4</sub> filler, which is present only in Kapton HN.<br/>

Combined experimental and triple-mode sorption modeling approach for sorption and diffusion in polymeric materials

2019 Fall National Meeting

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