A new kind of polyimide foams was successfully prepared using 3，3′，4，4′-benzophenone tetracarboxylic dianhydride (BTDA) and 4，4′-methylene dianiline (MDA) as main materials.First

BTDA diester was synthesized by esterification with methyl alcohol as a solvent.Subsequently

the polyamic ester precursor was polycondensated in the solution.Finally

polyimide foams were prepared through heating the precursor powder.The chemical structure of precursor powder

morphorlogy and size of cell

thermal properties and acoustical behavior of foams were characterized by Fourier transform infrared spectroscopy (FTIR)

1H nuclear magnetic resonance(1H-NMR)

scanning electron microscopy (SEM)

thermal conductivity measurer

thermogravimetic analysis(TGA)

differential scanning calorimetry (DSC) and standing wave tube，respectively.The results show that the precursor powder exists mainly as ammonium salt.Cells of the foams are uniform

and the cell size gets smaller with increase of drying temperature for precursor.The thermal conductivity λ of foams is 7.62×10-3 W/(m#8226;K)

temperature of 5 wt% weight loss is 540℃ and glass transition temperature Tg is 316℃

which reveals the favorable thermal properties.And it can be known that the sound absorption coefficient comes up to 0.79 while the soniferous loss reaches 19.4 dB at 0～2000 Hz

which indicates the foam has low frequency sound absorption and sound insulation properties.