Relationship Of The Sound Insulation Properties And Structure Parameters Of Melt-Blown Nonwovens

Noise is the third largest pollution produced by humans. With the economic development and the noise pollution becomes severe, how to shield or cut off the spread of noise and get high sound absorption material over a wide frequency band become one of the hot topics. There are two methods to reduce the noise which has been formed:sound insulation and sound absorption. To sound insulation, reflection is the most important which will cause multiple-pollution. At the same time, the cost of the material with a high density is high. In the other way, sound absorption technique is used to reduce the noise by acoustic energy dissipation. And the sound-absorbing and sound-insulation material which is porous has been the most widely using one to reduce the noise. Melt-blown nonwoven which is formed by the fiber assembly is the typical porous material. Due to ultra-fine fibers, simple process, recyclable and good stability, the melt-blown nonwoven materials have been concerned by public gradually in recent years.Sample were made on the traditional melt-blown machine and the structure of samples, such as thickness, bulk density, fiber diameter were tested. Several melt-blown nonwoven samples were tested through wave tube methods, and some factors such as fiber size, thickness, density, pore structure affecting in sound insulation properties were discussed. The sound insulations of gradient structures which were composed by samples with different porosities were tested.Through the study, it can be concluded as following:1. under constants of the other technological parameters, the distance to receive fiber determined the thickness, the thickness increased from0.31mm to0.41mm,while the distance enlarged from5cm to15cm; due to the increase of screw frequency, fiber size was lower, thicknesses and bulk densities were higher. Since the cycles were improved from4m/min to8m/min, thicknesses was increased1.94mm from0.72mm, the bulk densities were increased from62.3g/m2to250.8g/m2.2. The research results indicated that the thickness and density played more important roles in the sound insulation. While density kept on90kg/mJ, in thickness range of0.72-2.66mm. the relationship between thickness and sound insulation was linear correlation; thicknesses were same, the densities were changed in86.53-321.5kg/m, it was linear correlation between density and sound insulation.3. The finer fibers in nonwovens, the better sound insulation. In low frequency band(100-1000Hz), the effect to sound insulation was little; in high band(1000-6300Hz), sound insulation changed more.4. The reduction of porosity would be beneficial to improve sound transmission loss while the difference in porosities was large. The smaller the pore diameter and more uniform the pore size distribution, better sound insulation; on the other hand, the larger pore diameter and greater dispersion the pore size distribution, the worse the sound insulation.5. The gradient structure combined by melt-blown nonwovens with different porosities could effectively improve sound insulation in the low-frequency. The sound transmission loss were remained at a high position in the high-frequency (1000-6300Hz), up to22.4dB. At the same time, the curve of sound transmission was relatively flat. Combining the samples with different porosities from high to low was conducive to the improvement of sound insulation.