Sound attenuation in composite friction materials containing thermoplastic elastomers

Attempts have been made for the first time to modify and improve the sound attenuation ability of a friction material by the inclusion of combined plastic/rubber properties of thermoplastic elastomers (TPE) as viscoelastic polymeric materials, into the formulation. To evaluate the attenuation coefficient (α) and also the real part wave number (k') for the friction material, the viscoelastic parameters such as loss factor (tan δ) and elastic modulus (E') were measured by the use of dynamic mechanical analyzer (DMA). Styrene-butadiene-styrene (SBS), styrene-ethylene-butylene-styrene (SEBS) and nitrile rubber/polyvinyl chloride (NBR/PVC) blend system were used as TPE materials. However, SEBS and NBR/PVC were found to be much more effective in reducing the sound propagating speed as well as the sound level. All the friction materials containing TPEs exhibited more sound damping behavior at a wide range of temperature compared with the reference sample.