Preparation and sound absorption properties of barium titanate/nitrile butadiene rubber-polyurethane foam composites with stratified structure

Barium titanate/nitrile butadiene rubber (BT/NBR) and polyurethane (PU) foam were combined to prepare sound-absorbing materials with different stratified structures including a double-layer structure and alternating multilayered structure, respectively. The effects of the cell size of the PU foam and the thickness of the PU foam layer on the sound absorption efficiency of the BT/NBR-PU foam composite with a double-layer structure were studied, and the effects of the alternating unit number on the sound absorption efficiency of the BT/NBR-PU foam composite with an alternating multilayered structure were studied. The results show that the sound absorption peak of the double-layer structure composites would move toward low frequency with a decrease of the cell size of the PU foam or with an increase the thickness of the PU foam layer. With increasing alternating unit number, the composites with an alternating multilayered structure have good sound absorption performance in a wider frequency bandwidth. The sound absorption frequency range of the stratified composite could be adjusted by changing the cell size of the PU foam, the thickness of the PU foam layer and the alternating unit number. Each stratified structure BT/NBR-PU foam, whether with a double-layer structure or alternating multilayered structure, shows excellent sound absorption efficiency at low frequency owing to the combination of airflow resistivity, resonance absorption and interface dissipation.