| Nonwovens have a strong presence in the fabric market because of the high efficiency and low cost of producing them. Because of some special performances like three-dimensional structure, high porosity, and low mass, it is widely recognized that various industrial nonwoven products have a great potential in automotive, architectural, and shipping applications. In this thesis, the mechanical properties and acoustic performance of thermally bonded nonwovens are discussed. The effect of different fiber blend ratios and bulk densities at similar thicknesses on strength, air permeability, and sound absorption coefficient has been studied in this research. A thermal-conductivity box was designed in order to make uniform thermally bonded nonwovens with fixed thickness. Biodegradable and recyclable cotton, regular polyester, and bi-component fibers were used as the raw materials to make acoustic nonwovens through the air-laid and thermal bonding processes. The testing methods of mechanical and acoustic properties follow the relevant test standards from American Society for Testing and Materials. The test results showed that sound absorption coefficient of nonwovens increased significantly with the growth in frequency. In the low-middle frequency, the sound absorption coefficient increased with the increasing bulk density of nonwovens. And the noise reduction coefficient of20%polyester-60%cotton-20%bicomponent nonwoven (abbreviated NC) with lower bulk density was greater than the60%polyester-20%cotton-20%bicomponent nonwoven (abbreviated NP). The sound absorption coefficient of acoustic nonwovens with the surface with more loose fibers towards the sound wave was greater than the sample with the surface with fewer loose fibers towards the sound wave in the low-middle frequency region. And then the difference of sound absorption coefficient between the two samples decreased with the increase of frequency in high frequency region. |
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