Preparation And Properties Of Ultra-Fine Fiber Sponge For Low-Frequency Noise Absorption

With the rapid development of the global economy and technology,noise pollution is getting more and more serious,it has become a critical problem that threatens human health,both physically and mentally.At present,noise pollution has become a worldwide environmental problem,its sources can be found in every corner of our life,including transportation,manufacturing,house appliances,construction,and so on.Therefore,how to effectively control noise pollution becomes particularly important.Benefiting from the advantages like structural controllable,lightweight,easy preparing,and wide sound-absorbing frequency band,fibrous sound-absorbing materials are widely used for noise reduction.However,traditional fibrous sound-absorbing materials suffer from defects like large fiber diameter,low porosity,and small pore size,which results in poor low-frequency sound-absorbing performance.Electrospinning is a prospective technology for preparing micro and nanofiber materials,and it has the superiorities of easy preparation,low cost,wide source of raw materials,adjustable fiber structure,and so on.It has an extensive application prospect in the field of sound absorption and noise reduction.However,the electrospinning fiber materials are all densely packed,leading to a short acoustic propagation path and poor sound absorption property.Therefore,fabricating one kind of three-dimensional fluffy structured electrospinning fibrous material for sound absorption is of great significance.Herein,polysulfone(PSU)/polyurethane(PU)fibrous sponge with three-dimensional fluffy structure was prepared through high humidity assisted electrospinning technology.The properties of the fiber sponge were analyzed by scanning electron microscope,dynamic thermomechanical analyzer,and impedance tube test system.The optimal electrospinning parameters are as follows:solution concentration of 20 wt%,spinning voltage of 30 k V,the receiving distance is 25 cm and the revolving speed is 25 rpm.At the same time,the volume density of the fibrous sponge was only4.31 mg/cm~3,and the noise reduction coefficient is 0.509.By further adjusting the cavity depth during the sound absorption performance test,the results showed that increasing the cavity depth is conducive to the improvement of the sponges’low-frequency sound absorption performance.When the cavity depth is 35 mm,the noise reduction coefficient increases to 0.569.To further improve the stability of the three-dimensional fluffy structure,the cross-linking agent was introduced to construct the cross-linking network.Firstly,the cross-linking mechanism and effect ofγ-methylacrylloxy propyl trimethoxy silane(KH570),trifunctional group azopyridine cross-linking agent(TTMA),and blocked isocyanate polymer(BIP)were investigated respectively.The results showed that BIP could trigger the occurrence of in situ polymerizations between BIP and PU macromolecular chains,and the bonding structure between fibers,which can effectively enhance the mechanical properties of single fibers and fiber aggregates.Further investigated the optimal addition amount of BIP.When the content of BIP was 20 wt%,the breaking strength of PSU/PU/BIP fibrous sponges reached 478.7 k Pa,which was 128.3%higher than the original PSU/PU fibrous sponge without crosslinking.Meanwhile,PSU/PU/BIP fibrous sponges also have excellent fatigue resistance.After 100 times of cyclic compression,the plastic deformation was only6.51%.In addition,the cross-linking treatment did not damage the three-dimensional fluffy structure of the sponge,and the porosity of it was still as high as 99.54%after cross-linking.At the same time,the sound absorption stability of the fiber sponge was greatly enhanced.After 12 h of compression under 80%strain,the noise reduction coefficient of the fiber sponge decreased by only 3.5%.Subsequently,further investigated the different properties of fibrous sponge and commercial acoustic materials.Results showed that fiber diameter refinement can effectively improve the acoustic performance of the fiber material,and the fibrous sponge has significantly better acoustic performance than other commercial acoustic materials,while its gram weight was only less than one-half of that of the high-performance commercial products.Finally,the mass production of the fibrous sponge was initially discussed.Based on COMSOL Multiphysics software,the flow channel structure of the existing multi-nozzle electrospinning pipe was optimized.After optimization,the liquid discharge uniformity of the spinning nozzle was significantly improved,and the variation coefficient of the flow velocity of different discharge ports was only 3.34%.The result provided a new idea for the flow channel design of the new multi-nozzle electrospinning equipment.