Cyanate ester/polyhedral oligomeric silsesquioxane (POSS) nanocomposites: Synthesis and characterization

Cyanate ester (PT-15, Lonza Corp.) composites containing the blended polyhedral oligomeric silsesquioxane (POSS), TriSilanolPhenyl-POSS (C42H38O12Si7), were prepared containing PT-15/POSS 99/1, 97/3, 95/5, 90/10, and 85/15 w/w ratios. The composites were characterized by FT-TR, X-ray diffraction (XRD), small-angle neutron scattering (SANS), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (X-EDS), transmission electron microscopy (TEM), dynamic mechanical thermal analysis (DMTA), and three-point bending flexural tests. TriSilanolPhenyl-POSS was throughly dispersed into uncured liquid PT-15 resin. After curing, XRD, SANS, and X-EDS measurements were consistent with partial molecular dispersion of a portion of the POSS units in the continuous matrix phase while the remainder forms POSS aggregates. Larger aggregates are formed at higher loadings. SANS, SEM, and TEM show that POSS-enriched nanoparticles are present in the PT-15/POSS composites. The storage bending moduli, E, and the glass transition temperatures, T-g, of PT-15/POSS 99/1, 97/3, and 95/5 composites are higher than those of the pure PT-15 over the temperature range from 35 to 350 degrees C. The E' values for all these composites (except for the 15 wt % POSS sample) are significantly greater than that of the pure resin at T > T-g. Therefore, small amounts ( <= 5 wt %) of TriSilanolPhenyl-POSS incorporated into cyanate ester resin PT-15 can improve the storage modulus and the high-temperature properties of these cyanate ester composites versus the pure PT-15 resin. The flexural strength and flexural modulus are also raised by POSS incorporation.