Improving the Sound Absorption Properties of Flexible Polyurethane (PU) Foam using Nanofibers and Nanoparticles

Abstract

Polyurethane foam as the most well-known absorbent materials has a suitable absorption coefficient only within a limited frequency range. The aim of this study was to improve the sound absorption coefficient of flexible polyurethane (PU) foam within the range of various frequencies using clay nanoparticles, polyacrylonitrile nanofibers, and polyvinylidene fluoride nanofibers. The response surface method was used to determine the effect of addition of nanofibers of PAN and PVDF, addition of clay nanoparticles, absorbent thickness, and air gap on the sound absorption coefficient of flexible polyurethane foam (PU) across different frequency ranges. The absorption coefficient of the samples was measured using Impedance Tubes device. Nano clay at low thicknesses as well as polyacrylonitrile nanofibers and polyvinyl fluoride nanofibers at higher thicknesses had a greater positive effect on absorption coefficient. The mean sound absorption coefficient in the composite with the highest absorption coefficient at middle and high frequencies was 0.798 and 0.75, respectively. In comparison with pure polyurethane foam with the same thickness and air gap, these values were 2.22 times at the middle frequencies and 1.47 times at high frequencies, respectively. Surface porosity rose with increasing nano clay, but decreased with increasing polyacrylonitrile nanofibers and polyvinyl fluoride nanofibers. The results indicated that the absorption coefficient was elevated with increasing the thickness and air gap. This study suggests that the use of a combination of nanoparticles and nanofibers can enhance the acoustic properties of flexible polyurethane foam.

Recent Advances in Preparation and Structure of Polyurethane Porous Materials for Sound Absorbing Application

“…Hajizadeh et al have found that the use of a combination of nanoclay particles, polyacrylonitrile nanofibers (NFs), and PVDF NFs could synergistically improve the SAC of flexible PU foam by more than twice in the middle frequency region. [97] They have ascribed the phenomenon to the large specific surface characteristics of fillers. Tiuc et al have mixed synthetic textile fibers (including nylon, polyacril, and modal) with PU foam.…”

Experimental and numerical study of rigid polyurethane foams for mechanical characteristics using finite element analysis

“…The outer topography of the foams is almost open cell as the gases on the outer surface will have an atmospheric effect [20]. Few SEM analysis reports have shown that rigid foams are a combination of both open and closed cells in cell structure [21].…”

Research on Acoustic Absorption Properties of Aramid Honeycomb Composite Material Reinforced by Polyimide Foam

“…After the sound wave entered composite samples, due to the porous structure of IBPIF, the sound wave would continue to reflect and propagate inside, resulting in the vibration of the air inside the sample, causing friction between air molecules and friction between air molecules and the cell wall to convert a part of sound energy into heat energy. [30,[36][37][38] In addition, because IBPIF was filled in the separated core of ARHC, IBPIF was surrounded by honeycomb walls of pure aramid. Therefore, during the sound wave propagation, the honeycomb wall also played a certain role in reflection and increased the propagation path of the sound wave inside the sample, and finally achieved the absorption for the sound wave.…”