Preparation and properties of cyanate ester/polyorganosiloxane blends with lower dielectric loss and improved toughness

Novel modified cyanate ester resins (EPMPS‐n/BADCy), with significantly decreased dielectric loss and improved toughness, were developed by copolymerizing the cyanate ester resin, 2, 2′‐bis (4‐cyanatophenyl) isopropylidene resin) (BADCy), with an epoxidized methyl phenyl silicone resin (EPMPS). The curing behavior of EPMPS‐n/BADCy and the typical properties of the corresponding cured EPMPS‐n/BADCy were systematically investigated. The results show that the addition of EPMPS into BADCy can not only accelerate the curing reaction of BADCy, but also decrease dielectric loss and enhance the impact strength as well as water resistance. For example, in the case of the modified BADCy resin with 15 wt%EPMPS, its impact strength is 17.8 kJ/m², about 3 times of that of pure BADCy resin and its water absorption is only 0.25%, about one‐half of that of pure BADCy resin. In addition, while the dielectric loss is only 79% of that of pure BADCy resin, while its dielectric constant remains constant over the frequency range of 1KHz‐1 MHz. The above results suggest that EPMPS‐n/BADCy have great potential to be used as the matrix or adhesive for advanced composites. Copyright © 2009 John Wiley & Sons, Ltd.