CHARACTERIZATION OF HYDROLYTIC DEGRADATION OF U-F JOINTS THROUGH APPARENT DIFFUSIVITY

The hydrolytic aging of an adhesive joint (wood-urea/formaldehyde resi n) is characterized by measurements of the apparent diffusivity of two inert gases within the bond. This kind of measurement is of some inte rest, because it includes both chemical and geometrical changes in joi nt structure. Apparent diffusivities are determined in a diffusion cel l after various degradation times in a cold water bath. Our results sh ow that diffusivity increases with aging time with an asymptotic trend . Nevertheless, when the joint undergoes cyclic aging (immersion/dryin g), chemical degradation occurs mainly during the first cycle, while m echanical degradation observed during the drying steps also appears du ring the following cycles. The values of apparent diffusivity show tha t the solute transport is a real diffusional transport phenomenon and that resin joints are not porous.