(709f) An Experimental and Triple-Mode Sorption Modeling of Sorption and Diffusion in Polymers

An experimental and triple-mode
sorption modeling of sorption and diffusion in polymers

Hom N. Sharma, Stephen J. Harley,
Yunwei Sun, and Elizabeth A. Glascoe

Lawrence Livermore
National Laboratory

L288, 7000 East Ave.,
Livermore, CA 94550

925-423-5368

sharma@llnl.gov

Sorption and diffusion in polymeric materials is
of great interest in wide range of applications (e.g. electronic components to
microfluidics).(1-3) 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.

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(3) 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. We also show a simultaneous simulation of the transport
and chemical reactions of moisture through those example materials. Density
functional theory calculations are performed to investigate the impacts on
moisture uptake due to CaHPO₄ filler, which is present only in
Kapton HN.

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

Fig 1: 
Experiments and modeling results of dynamic moisture uptake by Kapton HN at a
range of relative humidities at 40.

References:

1.              Harley
SJ, Glascoe EA, Lewicki JP, Maxwell RS. Advances in Modeling Sorption and
Diffusion of Moisture in Porous Reactive Materials. Chemphyschem.
2014;15(9):1809-20.

2.              Harley
SJ, Glascoe EA, Maxwell RS. Thermodynamic Study on Dynamic Water Vapor Sorption
in Sylgard-184. J Phys Chem B. 2012;116(48):14183-90.

3.              Sun
YW, Harley SJ, Glascoe EA. Modeling and Uncertainty Quantification of Vapor
Sorption and Diffusion in Heterogeneous Polymers. Chemphyschem. 2015;16(14):3072-83.