Keywords: carbon nanotubes, polyurethane, nanocomposites, structural vibration, vibration damping, nanotechnology, CNT, DMA, dynamic mechanical analysis, FLD, free layer damping, viscoelastic
Carbon nanotube–polyurethane nanocomposites for structural vibration damping
Nanotechnology is an area which has vast potentials for turning fundamental research into successful innovations. In the present paper, damping in Polyurethane (PU)–Multiwalled carbon nanotube (MWNT) nanocomposites is studied by Dynamic Mechanical Analysis (DMA) and Free Layer Damping (FLD) methods. MWNT is functionalised using HNO3/H2SO4 mixture, thionyl chloride and ethylene diamine to introduce amide groups on the nanotube surface. Composites are prepared from a two–part PU resin system and the functionalised MWNT. The work addresses the concept of damping from molecular level interactions using DMA to an actual vibration damping technique, namely FLD. DMA study clearly shows a 70% increase of loss tangent of the nanocomposites as compared to neat PU, indicative of the high damping efficacy. The effectiveness of the developed nanocomposite is established by FLD measurements wherein a good damping of the order of 5–15 dB is observed in the frequency range of 10–1000 Hz, over that of neat PU. The added advantage of the system is the damping capability in the low frequency region also. The study is expected to be helpful in finding damping applications in aircraft and missile substructures, ships and submarines, machinery supports, mounting platforms of electronic equipment, bridges, buildings, etc.