With the depletion of petroleum resources, the development of traditional petroleum-based soundabsorbing materials (such as polyurethane foam, polystyrene foam) is gradually restricted, so the development of green sound-absorbing materials is particularly important. Plant fiber is a natural biodegradable biomass material, which widely exists in plants in nature and has abundant reserves. Rational use of such resources can reduce human dependence on nonrenewable raw materialssuch as petroleum.
Using plant fibers as raw materials has the advantages of degradability and reproducibility, and has broad application prospects in replacing traditional petroleumbased soundabsorbing materials. However, due to the relatively fluffy structure and rawmaterial properties of plant fiber foams, as well as poor mechanical properties and flame retardancy, their development is limited.
Silica sol is used to modify the soundabsorbing fiber, and through foam molding technology, lightweight, highstrength, heatresistant silica sol and plant fiber soundabsorbing materials can be quickly prepared. The amount of sol added has different effects on thedensity, mechanical properties, thermal stability and sound absorption properties of thematerial.
Silica sol is deposited on the surface of plant fibers to form an inorganic film, which can effectively delay heat transfer, prolong the final decomposition temperature, and improve the thermal stability of silica sol-plant fiber sound-absorbing materials. Compared with non-silica sol, the volume of silica sol-plant fiber sound-absorbing material is reduced, the inner compactness is improved, and the elastic modulus and yield strength are significantly improved. However, with the increase of silica sol, the density of sound-absorbing materials increases significantly, and too high addition of silica sol is not conducive to the lightweight of sound-absorbing materials.
Silicafree materials have the worst sound absorption. With the increase of silica sol
content, the sound absorption performance of the material first increases and then
decreases. This is because the sound wave is mainly diffracted into the interior of the
soundabsorbing material. When the internal porosity is too high, the flow resistance of the soundabsorbing material is small. The sound absorption effect is poor; when the porosityin the soundabsorbing material is too low, the sound wave is more likely to be reflected when it reaches the surface of the material and cannot enter the interior of the
soundabsorbing material, thereby reducing the soundabsorbing performance of the
sound-absorbing material. The addition of silica sol reduces the porosity of the sound-absorbing material, making its interior gradually denser. Considering the lightweight application of sound-absorbing materials, the density of sound-absorbing materials should not be too high. By optimizing the amount of silica sol
added, the best balance between pore structure and sound absorption performance
can be achieved.