Sound absorption behavior of flexible polyurethane foams including high molecular-weight copolymer polyol

Noise pollution is an important issue for automotive industries. In this article, the high molecular-weight copolymer polyol is blended in the polyol mixtures for fabricating flexible polyurethane foams to improve sound absorption efficiency. Changes of cavity size and material density of the foams are negligible by inclusion of copolymer polyol in the polyol mixture, but the closed pore ratio and specific airflow resistance increase for the copolymer polyol content higher than 20wt% because of changes of phase separation behavior from drainage flow rate reduction that occurs with increased viscosity. Sound absorption efficiency increases with increasing copolymer polyol content up to 20wt%, but it decreases beyond this point. The sound absorption property mainly results from the closed pore ratio, not from the cavity size. The compression strength increases with increasing copolymer polyol contents by increased amount of hard segments. Therefore, an optimum amount of high molecular-weight polyol is recommended for enhanced sound absorption property.