Water absorption kinetics
Generally, the water absorption behavior of polymers can be separated into four major behaviors, namely Fickian, relaxation controlled, pseudo-Fickian, and non-Fickian (anomalous) diffusion. The dominant mechanism depends on several factors such as chemical structure of the polymer, dimensions and morphology of the filler, and the polymer–filler interfacial adhesion [6, 15, 16]. The diffusion can be theoretically identified by the shape of the absorption curve represented by Eq. (4) [15].