Improving the sound absorption of a highly deformable nanocomposite foam based on ethylene-propylene-diene-monomer (EPDM) infused with multi-walled carbon nanotubes (MWCNTs) to absorb low-frequency waves

Abstract

In this study, an elastomeric nanocomposite foam was fabricated on the basis of ethylene-propylene-diene-monomer (EPDM) rubber filled with multi-walled carbon nanotubes (MWCNTs) to absorb low-frequency acoustic waves. The effects of adding MWCNTs on the cellular structure, viscoelastic behavior, and sound absorption characteristics were studied. Samples containing slight loadings of MWCNTs with increased damping factor and decreased pore sizes showed high viscose motions with superior sound absorption characteristic. The results revealed that the nanocomposite foam sample with only 0.1 phr (parts per hundred rubber) MWCNTs offered the best sound absorption coefficient with a sharp peak (0.98) within the frequency range of 500–1000 Hz. This can be justified by the dissipation of acoustic energy through vibration and deformation of the flexible cell walls due to the highly elastic matrix, high porosity and airflow resistivity of the fine partially reticulated cellular structure. With further MWCNTs loadings beyond the optimum level, the cell size was reduced dramatically, leading to reduction in porosity and excessive increase in air flow resistivity. These factors resulted in poor sound absorption feature. Moreover, the sound insulation performance of the nanocomposite foams was characterized, and it revealed the improving effect of MWCNTs, especially in high loading, by yielding a sound reduction index equal to 27–33 dB. According to the obtained results, the potential role of MWCNTs in the improvement of the acoustic absorption and sound insulation performance of EPDM foam can be inferred. Thus, a lightweight sound absorber with high resistance to harsh environmental conditions and excellent low-frequency sound absorption can be achieved by the infusion of nanoparticles.