Poly(propylene oxide) (PPO)-grafted nanosilica (NS)/polyurethane foam (PUF) composites were synthesized by a ringopening polymerization catalytic process and reaction-molding technology. The raw NS and PPO-NS were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and transmission electron microscopy. Scanning electron microscopy, dynamic mechanical analysis, and compressive strength tests were used to compare the morphology and thermal and mechanical properties of the PPO-NS/PUF and raw NS/PUF composites with a series of filler contents. The PPO-NS/PUF composites generally exhibited better morphology, thermal and mechanical properties than raw NS/PUF composites. Moreover, the PPO-NS/PUF composites with lower contents (0.5, 1 php) of filler showed even higher mechanical reinforcement than that with higher contents (1.5, 2 php) of filler, which was caused by the interaction between additives and PUF matrix.

A new type of cyanate (CE)/epoxy (EP) foam with bisphenol-A dicyanate ester prepolymer and diglycidyl ether of bisphenol-A (BADCy/DGEBA) has been successfully prepared through a two-step process. The structure and properties of CE/EP foam were studied. The results reveal that the CE/EP foams, with relatively uniform cell structure, were composed of closed cells as confirmed by scanning electron microscopy. The compressive strength increased from 0.507 MPa to 3.021 MPa, and the compressive modulus (E) increased from 15 MPa to 123 MPa as the density increased from 0.103 g cm À3 to 0.305 g cm À3. Dynamic mechanical analysis revealed that the CE/EP foams possessed a high glass transition temperature (T g ) (203 C) and that density had only a little impact on T g . Moreover, the excellent thermal stability presented with the onset of weight loss taken at 5% value was above 320 C, and the residual weight of the foam was more than 21.6% at 800 C. With increase in the density of CE/EP foams, the dielectric constants (") gradually decreased. For the foam with density of ¼ 0.162 g cm À3 , the value of " was as low as 2.28 at the frequency of 10 kHz.