Moisture absorption and hygrothermal aging in a bismaleimide resin

Moisture diffusion in a BMT resin has been investigated by submerging thin specimens in water. The weight gain of the neat resin deviates significantl y from Fick's law in that the uptake continues to slowly increase over an e xtended time scale. A two-stage diffusion model can successfully fit the ex perimental data. This model considers the structural relaxation induced by absorbed moisture, which is a good plasticizer of the resin. Desorption and re-absorption experiments indicate that the structural relaxation is irrev ersible upon desorption of water molecules. Dynamic mechanical analysis res ults demonstrate the plasticizing and rejuvenating effect of water. (C) 200 1 Published by Elsevier Science Ltd.