Sound absorption, Thermal and Mechanical behavior of Polyurethane foam modified with Nano silica, Nano clay and Crumb rubber fillers

Lot of research is going on in developing materials suitable for absorbing sound and reducing noise. By virtue of their superior vibration damping capability and attractive characteristics such as visco elasticity, simple processing and commercial availability polyurethane foams are extensively applied not only in automotive seats but also in various acoustical parts. However, the sound absorption coefficient of polyurethane foams is high (0.8 – 1.0) in high frequencies ranging from 300 to 10000Hz while it is found to be low (0 to 0.5) at low frequencies (10 to 200 Hz). In this study new polyurethane based porous composites were synthesized by in situ foam rising polymerization of polyol and diisocyanate in the presence of fillers such as nano silica, crumb rubber and nano clay. The effect of these fillers at various concentrations up to 2% was studied on sound absorption characteristics, thermal stability, and mechanical properties. Sound absorption coefficient was determined using standing wave sound impedance tube method. The sound absorption coefficient of filled PU foams is found to be increasing from 0.5 to 0.8 with increasing frequency from 100 to 200 Hz at higher content of the fillers employed. In addition to enhanced sound absorption properties in low frequency region, the composite foams exhibit superior thermal and mechanical properties. Further foam cell structure and size determined by using SEM and its effect on various properties will also be highlighted.