Improved Sound Absorption Properties in Polyurethane Foams by the Inclusion of Al₂O₃ Nanoparticles

Abstract

At present, the scale of China’s power grid is becoming larger and larger, and the control of low-frequency noise in substations (especially for transformers) is very important. The sound-absorbing materials have become one of the important ways to control low-frequency noise. The single polyurethane material cannot satisfy the requirements for reducing low-frequency noise, so it is very necessary to study its composite with other materials. In the paper, the flexible polyurethane foam and Al2O3 nanoparticle composites were obtained by the impregnation method. The method was simple, safe, and easy to control. The morphology and sound absorption coefficient of the foam materials before and after filling were analyzed. Single-hole acoustic cavity models of PU and Al2O3-PU composite were established through the finite element. The absorption and dissipation process of sound pressure for single hole was studied to understand the energy dissipation process. Meanwhile, through studying acoustic energy storage and acoustic energy dissipation, the loss factor of a single hole was obtained, which can predict the change rule of the sound absorption coefficient for PU foam and Al2O3-PU.

Simultaneous decolorization of anionic and cationic dyes by 3D metal-free easily separable visible light active photocatalyst

“…3a , it can be observed that the pure PUF has a highly porous 3D-hierarchical structure made up of open pore channel similar to a polyhedral model and inter-connecting framework. This morphology is similar to that previously reported in the literature (Farukh and Dhawan 2016 ; Gavgani et al 2016 ; Yuan et al 2021 ). Figure 3b shows that the as-prepared UGCN exists as large aggregates composed of several ultrathin layered two-dimension sheets with a thickness of few nanometers and irregular slightly curled edges.…”

“…On the other side, the XRD pattern of pure PUF shows the presence of a broad peak at 20.4° which indicates the amorphous nature of the prepared PUF. Notably, the obtained XRD pattern is typical for isocyanate-based PUF (Farukh and Dhawan 2016 ; Kim et al 2018 ; Yuan et al 2021 ). The composite material (PUF/UGCN) has three diffraction peaks at 13.5°, 19.0°, and 27.2°.…”

Theoretical and experimental study on sound absorption performance of Al2O3-polyurethane foam and microperforated plate composite structure

“…The Al 2 O 3 -PU composites were prepared according to the research methods previously published by our team 13 The Al 2 O 3 -PU foam and plexiglass were bonded by the epoxy resin and curing agent with a ratio of 5:1, and then was dried naturally for more than 12 h. The diameter of composite structure was 100 mm, and the thickness of plexiglass was 5 mm. The spacing of holes with a diameter for 2 mm on the perforated top cover was 10 mm, and the perforation rate was 2.44%.…”

“…The air part of the pipe was endowed with air characteristics, and the sound-absorbing material part was endowed with Al 2 O 3 -PU porous foam properties. The parameters of Al 2 O 3 -PU foam were as follows: porosity 0.704, flow resistance 70,000 N·s·m −4 , tortuosity factor 1.34, viscosity characteristic length, 1.99 × 10 −5 m, thermal characteristic length 4.64·10 −5 m. 13,14 A perfect matching layer was applied to the left air region. And each small hole of the regular plexiglass circular plate was filled with an air column.…”

“…In our previous work, 13 Al2O 3 -PU composite was prepared and its sound absorption performance was improved. Meantime, based on microscopic single-hole model, the loss factor was calculated through investigation the sound energy storage and sound energy dissipation process.…”