Water uptake effects in resins based on alkenyl-modified cyanate ester-bismaleimide blends

The analysis of cured resin blends comprising a commercial dicyanate, bisma leimide and a range of novel alkenyl-substituted cyanates, to determine the chemical effects of long-term exposure to water, is reported. The cured re sin blends underwent accelerated water uptake by immersion at temperatures of 50 degreesC and 70 degreesC, for a period of 14-17 months. The presence of about 10-15% (by weight) of alkenyl-substituted cyanate in the blend lea ds to a marked reduction in moisture absorption in comparison with the unmo dified bismaleimide/cyanate blend containing a comparable amount of bismale imide. All samples display non-Fickian diffusion behaviour at both immersio n temperatures, although this is most marked at the higher temperature. The rmogravimetric analysis was performed on alkenyl-modified neat resin sample s before and after the immersion period. The modified samples display therm al stabilities that are indistinguishable from cured resins that have not u ndergone immersion. Spectroscopy (near infrared Raman and mid-infrared atte nuated total reflectance) was performed on cured resin plaques to determine the sample composition as a function of modifier content. The elemental co mposition of the samples was also determined before and after the immersion period, and no significant variation in elemental composition was recorded for the modified samples. (C) British Crown Copyright 2001/DERA. Reproduce d with the permission of Her Majesty's Stationery Office. Published for the SCI by John Wiley & Sons, Ltd.