Study On Perparation And The Sound Absorption Properties Of Rate Sensitive Materials Modified Polyurethane And Ethylene Vinyl Acetate Foam

Foamed polyurethane(PU)and foamed ethylene-vinyl acetate copolymer(EVA)have a special cell structure and good viscoelastic damping characteristics so that they can absorb as much sound energy as possible,and are widely used in absorption Acoustic noise reduction field.However,the sound absorption coefficient of PU and EVA foam materials needs to be further improved,especially in the low-frequency region,which has the disadvantage of poor sound absorption performance.Shear Thickening Fluids(STFs)made of silica(SiO₂)particles and polyethylene glycol(PEG-600)and Polyborosiloxanes(PBDMSs)all show rapid changes in properties in response to external alternating stress,accordingly absorbing and dispersing energy.Therefore,this article first prepared PBDMSs and STFs,and studied the rheological properties of PBDMSs and STFs;Secondly,use PBDMSs and STFs to control the cell structure of PU and EVA foam and improve its own viscoelastic damping performance,and study the relationship between its cell microstructure,damping performance and sound absorption performance;Finally,the influence of PBDMSs and STFs on the sound absorption performance of PU and EVA foam materials is summarized,and it is expected that sound absorption and noise reduction foam materials with application value will be obtained.The results show that when PU foam material is added to STFs,the sound absorption performance is improved to a certain extent,and the sound absorption curve shifts to low frequency.The PBDMSs effectively improved the sound absorption performance of EVA foam,and the sound absorption peak shifted to low frequency.This makes STFs modified PU foam materials and PBDMSs modified EVA foam materials have certain application potential in sound absorption and noise reduction.The main research results of this paper are as follows:The rheological results of PBDMSs showed that the viscosity of PBDMSs remained almost unchanged before the shear rate reached 0.1 s^-1,and then began to decrease.As the frequency increases,the storage modulus increases from 2089 Pa to 60000 Pa and then remains unchanged,while the loss modulus first increases from 10750 Pa to 29300 Pa and then decreases to 1260 Pa.STFs viscosity is mainly affected by SiO₂ content.The more SiO₂ content,the greater the viscosity.STFs with different SiO₂ content all show shear thinning and thickening.As the content of SiO₂ in STFs increases,the critical shear rate of STFs gradually decreases(from 26.56 s^-1 to10 s^-1),while the peak viscosity gradually increases(from 1.52 Pa·s to 157 Pa·s),and the critical shear frequency of liquid-solid transition also gradually increased(from 7.49 Hz to 23.71 Hz).Among the PU foam materials modified by PBDMSs,PBDMSs causes the open cell ratio of PU foam to decrease,which has a negative impact on the sound absorption performance.The maximum sound absorption coefficient is reduced from 0.44(pure PU)to 0.27,and the sound absorption curve does not shift.When using STFs to modify PU,with the increase of SiO₂ content in STFs,the closed cell ratio gradually increases,TA(Tan?-T curve enclosing area)gradually increases,the damping performance increases,the sound absorption coefficient of PU foam gradually increases,and the sound absorption curve moves to the low frequency region.Among them,STFs-40(40%SiO₂ content)modified PU foam has the best sound absorption performance.Its maximum sound absorption coefficient has been increased from 0.84(pure PU)to 0.99,and the first resonance frequency has moved from 3728 Hz(pure PU)to 2176 Hz.When EVA is modified with PBDMSs,with the increase of PBDMSs content,the average cell diameter gradually decreased,from 66.83?m(pure EVA)to 43.6?m(8%PBDMSs).When the amount of PBDMSs added is 8%,the sound absorption coefficient of EVA composite foam is the largest,increasing from 0.19(pure EVA)to 0.48,and the maximum sound absorption coefficient is increased by 43.28%.Aa well as,after modification,the first resonance frequency shifts to the low frequency region.PBDMSs significantly improve the sound absorption performance of 1000 Hz?2000 Hz.As the content of PBDMSs increases,the TA of the EVA foam increases slightly,and the damping performance is improved to a certain extent.The increase in the sound absorption coefficient is mainly caused by the reduction of the cell size,and the damping loss contributes less to the sound energy loss.