Graphs were plotted against -ln (Qe - Qt) and t (Fig. 3(a2)) to ex-amine the above kinetic model. Swelling rate constant (k) and can be obtained from the slope of the line while theoretical equilibrium swelling was calculated form intersection of the lines. The results are summarized in Table 3. It is showed that experimental results are close to theoretical data, which confirms that the swelling process of WPU coatings is consistent with kinetic first-order equation. Moreover, there is gradual increment in k, which may due to enhanced entanglement of soft segments and hard segments contributing to a low crystalline network, thus allowing water molecules to penetrate easily.