Preparation And Performance Study Of Porous Aerogel Sound-absorbing Material

In order to solve the traditional sound-absorbing materials such as 3M acoustic cotton waste due to non-degradable and other problems caused by serious environmental pollution,research and development of green recyclable and degradable sound-absorbing materials is extremely urgent.Cellulose aerogel not only has the advantages of high porosity and small pore size of aerogel,but also has the characteristics of renewable and biodegradable.However,the closed pore structure of conventional cellulose aerogel is the key factor that hinders its sound absorption performance.Therefore,we use directional freezing to modulate the gel structure to obtain an open porous structure to solve the problem of non-absorbable aerogel.And in situ synthesis of magnesium hydroxide nanoparticles in cellulose hydrogel structure to solve the problem of flammability of the material while improving the sound absorption.Finally,the doped polyvinyl alcohol staple fiber constructs the fiber-doped porous structure to improve the low and medium frequency sound absorption of the material.The composite cellulose aerogel prepared in this study has good sound absorption properties,compression properties and flame retardant properties.Firstly,cellulose hydrogels were prepared from cotton pulp board,and cellulose aerogels with regular distribution and axially open porous structure were prepared by using directional freezing method to treat the hydrogel network structure.The effects of adding different mass fractions of cotton staple on the sound absorption and compression properties of the cellulose aerogels were investigated.The prepared directional cellulose aerogel achieved a sound absorption coefficient of 0.88 at 4500 Hz and a noise reduction coefficient of 0.35.In addition,the directional cellulose aerogel had good compressive properties,reaching a compressive stress of 0.35 MPa at a strain of 70%.Secondly,to solve the problem of combustibility of cellulose aerogels,magnesium hydroxide nanoparticles(MH NPs)doping was used to prepare magnesium hydroxide nanoparticle-loaded directional cellulose aerogels.The effects of different concentrations of magnesium chloride solutions on the sound absorption,flame retardancy and compression properties of MH@ cellulose aerogels were investigated.The results showed that the MH NPs were uniformly dispersed in the cellulose aerogel and had no significant effect on the porous structure,and the noise reduction coefficient was improved to 0.39.The flame retardant properties of the prepared MH@cellulose aerogel were significantly improved,and the material was self-extinguished within 5 s after ignition.In addition,the compressive strength was improved by nearly two times,reaching 0.72 MPa at 70% strain.Finally,in order to enhance the low and medium frequency sound absorption properties of magnesium hydroxide cellulose aerogels,polyvinyl alcohol short fibers/magnesium hydroxide secondary doped directional cellulose aerogels were prepared.The effects of adding different masses of polyvinyl alcohol short fibers on the sound absorption properties and compression properties of the aerogel were investigated.The results show that the fiber-doped porous structure has a large improvement on the sound absorption performance in the frequency range of 500-2500 Hz,and the noise reduction coefficient reaches 0.46.The flame retardant performance of the material is slightly reduced,and it is self-extinguished within 40 s.And the stress reached 1.107 MPa at 70% strain.The research in this thesis may provide a new strategic direction for the development of green sound-absorbing materials.