Moisture absorption measurement and modelling of a cellulose acetate
2021
Khoshtinat, S. | Carvelli, V. | Marano, C.
With a view toward the application of highly hygroscopic polymers as a humidity responsive self-actuator, the evaluation of the real time moisture concentration in the material becomes a priority. In this paper, the moisture diffusion process in a cellulose acetate (53.3% of acetylation) has been studied. Membranes of cellulose acetate (thickness within the range 66–200 µm) have been prepared, and the moisture absorption at room temperature and at a different relative humidity (RH within the range 21–53%) has been monitored. An analytical model has been used to describe the observed non-Fickian sigmoidal behavior of moisture diffusion. A relaxation factor (β) of about 0.026 s⁻¹ and a moisture diffusion coefficient (D) of 3.35 × 10–⁶ mm²/s have been determined. At constant room temperature, the moisture concentration at saturation (Cₛₐₜ) has shown a linear relation with relative humidity. The identified values β, D and Cₛₐₜ of the analytical model have been used as input for the finite element simulation of the non-Fickian diffusion. The reliability of the finite element simulations has been confirmed with a second set of experiments.
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