Development of cell morphologies in manufacturing flexible polyurethane urea foams as sound absorption materials

The effect of water content and a type of gelling catalysts [Triethylenediamine (DABCO) and dibutyltin dilaurate (DBTDL)] on chemical and physical structures of the flexible polyurethane foams (the flexible PUFs) is explored by a fourier transform infrared spectroscopy with attenuated total reflectance and a scanning electron microscope techniques. The amount of water usage plays a crucial role in controlling the sizes of cavities and pores of the PUFs. From the two gelling catalysts, the DBTDL reduces the rate of urea formation and NCO (isocyanate functional group) conversion due to the reduced molecular activity from the sterically hindered catalyst structure, comparing with the DABCO catalyst case. Strong gelling effect of the DBTDL can prevent the coalescence of the cavities and thus produce high number of well dispersed pores, but poor cavity and pore morphologies are observed in case of the fast reactions between isocyanate and water with the DABCO catalyst. The size uncertainties of cavity and pores with DBTDL catalyst are relatively smaller than with DABCO catalyst. In the sound absorption characteristics, uniformly distributed cavities and pores show better efficiency than the non-uniform cases.