Sound absorption properties of rigid polyurethane foam composites with rubber-wood sawdust as a natural filler

Abstract

Rigid closed-cell polyurethane (PU) foam is well-known for its ability to withstand external force. On the other hand, due to the closed-cell nature, its ability to absorb sound is doubtful since hollowed materials are supposed be better in sound absorption. However, the composites fabrication with non-reactive fillers was thought to improve sound absorption ability since it might prohibit the formation of closed cell in the process. In this research, rigid polyurethane foam was prepared from polyether polyol and polymeric methylene di-isocyanate (p-MDI) formulated with water as a blowing agent. Natural rubber-wood sawdust was used as a filler. The percentages of rubber-wood sawdust in the polyurethane foam composites were varied by 0, 1, 3, 5 and 7%. The measurement of sound absorption coefficient has been done using impedance tube technique. The results showed that the rigid closed-cell polyurethane foam with 0% filler exhibits poor acoustic absorption. Additionally, sound absorption coefficient results showed that a sample with higher amount of rubber-wood sawdust allowed the sound wave to be absorbed at wider frequency range. This could be explained that the rubber-wood sawdust filler played an important role in sound absorption property.