Sound absorption properties of carbon nanotube-Polyurethane composite films
Sheik Mohamed Anees Shiek Abdul Farook
Date of Issue2016
School of Materials Science and Engineering
Increase in road traffic and construction noises demonstrates the importance for developing sound absorbing paints for the painting of residential buildings to reduce disturbance to residents. Developing such paints requires sound understanding of the sound absorption mechanism which has not been well established by past studies. This study wishes to test its hypothesis that the secondary interactions are the main governing force behind the sound absorption mechanism. To accomplish that, this study adds carbon nanotubes (CNTs) into a polyurethane matrix as a means of manipulating the secondary interactions within the matrix. Thereafter, this study investigates if a correlation between the sound absorption properties and the dynamic mechanical behaviour can be found, thereby proving that the sound absorption is indeed governed by secondary interactions. Furthermore, optical micrographs were taken to observe the dispersion of the CNTs. Tensile testing and differential scanning calorimetry were also done to check if similar conclusions on the effect that CNTs have on the polymeric matrix are obtained when compared with those obtained from dynamic mechanical analysis and sound absorption testing. The main peak in the sound absorption curve shifted right as more CNTs were added up to a loading of 0.1wt% suggesting an increase in strength of the secondary interactions. Thereafter, addition of CNTs did not shift the peak any further. Similarly, tensile testing results proved that the reinforcing effect that CNTs provided was only up to 0.1wt% loading and thereafter the mechanical properties deteriorated. Analysis of optical micrographs proved that this could be attributed to the significant aggregation occurring for samples with more than 0.1wt% loading. Dynamic mechanical analysis(DMA) showed that there is an increase in number of interactions rather than strength as suggested in the sound absorption curves but this could be because, the peaks in the DMA represents different transitions as opposed to the peak in the sound absorption curve. A temperature sweep in stress relaxation mode however reveals a curve similar to the sound absorption curve suggesting their correlation. In conclusion, this study has not directly proven that secondary interactions are behind the sound absorption mechanism but has shown signs suggesting their correlation and paves the way for future studies to make that establishment.
Final Year Project (FYP)
Nanyang Technological University