The effect of stress whitening on moisture diffusion in thermosetting polymers
The effects of stress whitening on the moisture diffusion rate and concentration in a polymer adhesive containing a secondary phase were investigated. This was accomplished by performing an absorption test on both stress whitened and virgin samples of the bulk adhesive and comparing the rate and amount of moisture diffusion in each. The presence of stress whitening in samples was not only observed visually, but also confirmed analytically using the “Bilinear RAMOD-2” equation. Experimental results reveal that visibly-present stress whitening resulting from fracture does indeed affect the rate and amount of moisture absorption in a polymer adhesive. Consequently, a diffusion model representing two different regions, stress-whitened and non-stress-whitened, is proposed for path of diffusion in polymer adhesives.