Abstract: Two kinds of silica (SiO2) nanospheres were introduced into rigid polyurethane (PU-R) forming PU-R/SiO2 composite foams. Morphology of the composite foams was characterized by SEM. Mechanical properties, dimensional stabilities, and thermal conductivities of the composite foams were investigated by compressive test, dimensional stability test, and thermal conductivity measurements, respectively. It showed that, the cellular size of the composite foams was lowered obviously (from 303 μm of neat PU-R foam to 170 μm of the composite foam), the compressive properties were improved effectively (the specific compressive strength and specific compressive modulus increased by 8.3 % and 12.5 %, respectively, compared with those of neat PU-R foam), the coefficient of linear thermal expansion was decreased, the thermal conductivity was reduced slightly, and the dimensional stabilities almost keep invariable, after the introduction of SiO2 nanospheres. In addition, compared with 400 nm sized ones, 700 nm sized SiO2 nanospheres could be dispersed more homogeneously, and lead to better mechanical properties.

Key words: rigid polyurethane, foam, silica, nanoparticle, morphology, mechanical property, thermal conductivity