Phase separation behavior of cyanate ester resin/polysulfone blends

The composition of the blends and the curing temperature affect the morphol ogy of the blends and the phase separation mechanism. The phase separation mechanism depends on the viscosity of medium at the initial stage of phase separation determined by the amount of thermoplastics and the curing temper ature, and is closely related with the final morphology. When the homogeneo us bisphenol A dicyanate (BADCy)/polysulfone (PSF) blends with low content of PSF (less than 10 wt %) were cured isothermally, the blends were phase s eparated by nucleation and growth (NG) mechanism to form the PSF particle s tructure. On the other hand, with more than 20 wt % of PSF content, the BAD Cy/PSF blends were phase separated by spinodal decomposition (SD) to form t he BADCy particle structure. With about 15 wt % of PSF content, the blends were phase separated by SD and then NG to form a combined structure having both the PSF particle structure and the BADCy particle structure. (C) 1999 John Wiley & Sons, Inc.