Polyurethane (PU) is a polymer often used in underwater acoustics due to its water-like acoustic properties and good resistance to low temperatures, sea water ageing and salinity. The full characterization of PU is challenging and especially that of its shear modulus. In this context, we propose two ultrasonic measurement methods with a precise temperature control in order to identify the dynamic behavior of PU. On the one hand, we have adapted the � anvil � technique used to characterize fluid rheology, to determine the shear modulus of PU. This technique is based on the measurment of the reflection coefficents of shear horizontal waves at oblique incidence. On the other hand, measurements in transmission in immersion are peformed in order to determine the bulk modulus of the PU. With the help of the temperature control, the time-temperature superposition principle is studied. That allows to determine the rheology of the PU over a wide frequency band and fractionnar derivative models are then used to describe this rheology.