Effects of Crushing Process and Aging Time on the Sound Absorption Properties of Polyurethane Foams

Polyurethane foams are widely used as sound absorbing materials for automobiles due to their high sound absorption efficiency. The effects of crushing process and aging time on the sound absorption properties of polyurethane foams are investigated. The cavity and pore (open & closed) sizes are uniform regardless of the crushing process and aging time. However, the partially-open pore size decreases with increasing aging time. Closed pore ratio decreases, but the partially-open pore ratio increases with increasing aging time at the similar level of the open pore ratio. This is attributed to the increased partially-open pores derived from the closed pores by the crushing process. Sound absorption properties show maximum performance at 16 h of aging time, and these are strongly related to the airflow resistivity and tortuosity of polyurethane foams. Storage and loss modulus increase with increasing aging time, and it is closely related to the phase separation of polyurethane foams.