| Isocyanate-based Polyimide Foam(IBPIF)is a kind of foam with excellent physical and chemical properties.It has high temperature resistance,good flame retardancy,low smoke,radiation resistance,heat insulation and other properties.Although after several years of research,IBPIF materials based on free foaming technology have been far ahead of foams such as polyurethanes and melamines in terms of safety,but there is no relevant research report on the acoustic properties of IBPIF materials.As a result,IBPIF materials still have a large gap between the sound absorption performance and foams such as polyurethane and melamine,which greatly limits the application of this relatively good safety-based polymer-based foam in the sound-absorbing field and seriously hinders the material.development of.The free foaming preparation technology is a kind of technical approach that can quickly realize the industrialized production of polyimide foams.If it can keep the basic preparation formula of the materials unchanged,it can be simply passed through the use of additives and the foaming temperature environment.The change of technical links enables effective regulation of the cell's cell structure to achieve free and effective control of its acoustic performance.The purpose of improving the acoustic performance of IBPIF is to further broaden the application of polyimide foam.By regulating the amount of surfactant and foaming agent in the foaming white material,IBPIF materials having significantly different microscopic cell structure and sound absorption properties were prepared.The analysis results show that the surfactant is very important for the formation of a uniform and delicate cell structure,and with the increase of the amount,the pore size of the IBPIF material first decreases and then increases,and the open porosity gradually decreases,when the surfactant dosage is 18.75 wt%.The noise reduction coefficient of the prepared IBPIF material can reach 0.63.With the increase of foaming agent dosage,IBPIF's cell size gradually increases,and the open porosity rate increases gradually,and the flow resistance rate decreases.When the foaming agent dosage is 15.75 wt%,the IBPIF material has the highest noise reduction coefficient,which can reach 0.68.The IBPIF materials with different micro-cellular structures and sound absorption properties were prepared by controlling the initial foaming slurry temperatures at-10,0,10,20,30,and 40°C.When the slurry temperature is 0 °C,the sample has the best sound absorption performance in the frequency range of 315-630 Hz.When the slurry temperature is 40 °C,the sample has the best sound absorption performance in the 630-6300 Hz frequency band,and the frequency is 1 cm thick.The characteristic absorption sample was laterally combined with the low frequency characteristic absorption sample of 4 cm thick as the receiving surface,and a 5 cm thick combination sample with excellent sound absorption performance at 315-6300 Hz was obtained,and the noise reduction coefficient reached 0.68.By introducing nano-silica particles as the inorganic nucleation aid in the foaming slurry,a heterogeneous nucleation mechanism was introduced during the foaming nucleation stage of the mixed slurry,thereby changing the micro-cellular morphology and the sound absorption performance of the IBPIF material.When the foaming white material was used as the nano-silica dispersion system to prepare 1.4 wt% doping amount of SP30/IBPIF material,the particles could be dispersed evenly,and the pore diameter could be reduced,and the pore size distribution narrowed and opened.The microporous cell structure with a moderate cell porosity,in which the cell opening rate increased by 0.31%,and the noise reduction coefficient was 0.682,increased by 9.3% relative to the blank material. |
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