Preparation And Study Of Plant Fiber-based Porous Sound-absorbing Materials

In recent years,as global environmental problems have become increasingly prominent,more and more attention have been paid to the research and application of green,low-carbon and environmentally friendly materials.Traditional sound-absorbing materials are mainly made of glass fiber,mineral fiber,polyester fiber,etc.These materials are difficult to degrade,which not only harms the ecological environment,but also seriously affects human health and brings serious economic losses.The plant fiber,as a high-yield,green and degradable raw material,has gradually become the current research hotspot of new-type sound-absorbing materials with the demand for new-type degradable sound-absorbing materials.Although the sound absorption performance of the sound-absorbing material made of plant fiber is equivalent to that of the traditional sound-absorbing material,due to the characteristics of the fiber itself,there are problems of poor flame retardancy,no moisture resistance,and difficulty in mass production,which limits its practical application.In view of the current problems of plant fiber sound-absorbing materials,this study proposes a new technology in wet molding technology-foam forming technology,and uses silica sol to modify plant fiber to improve its high thermal stability,high porosity,and sound absorption performance.In foam forming technology,foam replaces water as a carrier for fibers and other raw materials.The fibers are separated by foam,which makes the molded material more fluffy and meets the basic characteristics of sound-absorbing materials.The specific research content and conclusions are as follows:(1)The influence of system concentration,fiber length,and surfactants on the foamability and foam stability of plant-based foam materials was analyzed.The results show that compared with hardwood fiber,softwood fiber is more conducive to stabilizing the foam and prolonging the half-life of the foam in the foam forming system.The 1.5% of fiber concentration is the best condition,which can not only achieve high foam stability,but also meet the requirements of preparing materials with high porosity structures.The surfactant experiment shows that under the active agent system of SDBS,the surface tension and viscosity of the slurry are as low as37.106 m N/m and 117.6 m Pa·s,at this time,the foaming volume is as high as 640 m L,and the discharge half-life is 6.5min,which is most suitable condition for foam forming process.(2)By using the optimized foam molding process parameters,a porous and lightweight plant fiber foam sound-absorbing material was prepared,and the macro and micro surface morphology,chemical structure,thermal stability,moisture resistance,mechanical properties and sound absorption performance are analyzed.The results show that an inorganic film is formed on the surface of the modified plant fiber,which improves the thermal stability of the material.When the amount of silica sol added is 8%,the density of the material is only 20.21kg·m-3,while the elastic modulus and yield strength are increased from 15.4KPa and 1.4KPa to 86.2KPa and 4.4KPa,respectively,an increase of 459.8% and 214.3%,and the sound absorption coefficient reached 0.65 above 5000 Hz.(3)The density and thickness of the material will affect its sound absorption performance.As the density or thickness increases,the sound absorption performance of the material gradually improves and finally stabilizes,and the first resonance frequency of the material moves to the low frequency direction.The fixed parameters in the Delany-Bazley model are determined by the double thickness method to verify the degree of fit with the plant fiber-based porous sound-absorbing material.The results show that the model fits the plant fiber-based porous sound-absorbing materials in this article to a high degree.The average absolute error between 200-6300 Hz is only 3.2%.The refitted model can provide theoretical guidance for the subsequent sound-absorbing materials in this article.In summary,the plant fiber-based porous sound-absorbing material prepared by the foam forming technology in this subject has a stable preparation process,high strength,heat resistance and moisture resistance,and excellent sound absorption performance.The plant fiber modified with silica sol makes up for its shortcomings of poor thermal stability and low strength.After verifying the applicability of the Delany-Bazley model to plant fiber-based porous soundabsorbing materials,the application of the sound-absorbing model in foam forming technology was supplemented,laying a foundation for the subsequent development and application of plant fiber-based porous sound-absorbing materials.