Preparation,structure, and properties of flexible polyurethane foams filled with fumed silica

Flexible polyurethane (PU) foams with different loading mass fraction (0%–2.0%) of fumed silica were synthesized by free-rising foaming method. The addition of 1.4% fumed silica makes the cells diffuse more uniform in the PU foam and the temperature of degradation occurring with a maximum weight loss rate is about 7 °C higher than that of pure PU foam. Most significantly, the sound absorption peaks of the filled PU foams shift to the low frequency region (from 997 Hz to 711 Hz) with increasing fumed silica content (0%–2.0%). The average sound absorption coefficients of filled PU foams increase except the content of 0.35% fumed silica. The experimental results show that flexible PU foams filled with fumed silica have excellent sound absorption characteristics in low-frequency regions.