Role of Elastic Modulus on the Acoustic Transmission Loss of Polypropylene/Barium Sulfate/Calcium Carbonate Nanocomposites with Microfiller/Nanofiller Bimodal Size Distribution

Highly-filled polymer composites have proven to be good noise-control materials. The viscoelastic polymer matrix functions as a good sound absorber and the high loading of fillers guarantee a high density composite which acts as a sound insulator. Sound insulation of materials is controlled by their density and elastic modulus. Although the role of density on the acoustic insulation of materials is well understood, the role of elastic modulus remains to be further illuminated. The addition of micron sized high density fillers provide a high density composite, but the elastic modulus, though increased to some extent, will not drastically improve to lead to a considerable augmentation in the acoustic transmission loss (acoustic insulation). A nanocomposite with a bimodal size distribution of micro and nanofillers encompass a high enough density and an elevated elastic modulus. In this study, role of elastic modulus on the transmission loss of polypropylene/micrometric barium sulfate/nanometric calcium carbonate nanocomposites has been investigated. The acoustic transmission loss has been measured using a 4-microphone standing wave duct. A new model based on Alembert’s equation for the transmission loss of materials has been developed and used to validate the results. The results show that replacing part of the microfillers with nanofillers causes a considerable increase in the elastic modulus of the composites which, respectively, leads to an augmentation in its acoustic transmission loss. The obtained results are in good agreement with the modified Alembert’s model.

Keywords:

Nanocomposite , acoustic transmission loss , elastic modulus , 4-microphone standing wave duct