ABSORPTION OF WATER BY POLYURETHANE FOAM - MODELING AND EXPERIMENTS

Polyurethane (PU) foams are made of small cells, regular in shape, which result from the presence of a gas acting as a blowing agent during its formation (carbon dioxide or fluorocarbon). When the PU foam is in contact with water, a matter transfer is observed, water diffusing into the foam. The presence of the blowing agent in the cells is responsible for hindered diffusion of the water. The same PU foams are immersed in water and dried; the process of absorption-desorption repeated many times shows a change in the diffusivity for the following stages of absorption. The diffusivity is considerably lower for the first absorption than for the following absorptions. Moreover, a finite coefficient of matter transfer is observed for the first absorption, while this coefficient is very high with the following absorptions.