S.F. Bartolucci, J.A. Maurer
U.S. Army RDECOM-ARDEC,
Keywords: carbon nanotube, nanocomposite, superhydrophobic, self cleaning, laser pulse heating
Summary:Polymers and polymer nanocomposite degradation has been studied under conditions of extremely high heating rates. Traditionally, carbon nanotubes and nanoclays have been added to polymers to impede the thermal degradation during slow heating rates (on the order of 10 C/min) typically experienced in thermogravimetric analysis and flammability research. In this study, we have examined how polypropylene-nanoclay (montmorillonite) and polypropylene-carbon nanotube nanocomposites behave when subjected to heating rates that are five orders of magnitude higher during irradiation with a 1064 nm Nd-YAG variable pulse millisecond laser. Mass loss data was collected for each sample, as well as post-mortem surface characterization using spectroscopy and electron microscopy. The analyses demonstrate that the nanospecies are effective in providing a protective surface barrier that decreases the amount of degradation and mass loss to the underlying polymer material. In addition, after laser pulse heating the carbon nanotube composites displayed superhydrophobicity and self-cleaning properties. Laser treatment exposes a carbon nanotube network which controls surface wetting properties. Advancing and receding contact angle measurements demonstrate that these surfaces are superhydrophobic. The use of simple pulsed laser heating to produce nanotube networks provides a cost-effective method for generation of superhydrophobic materials. The development of low-cost scalable technology for self-cleaning surfaces, such as described here, is critical to next generation materials in wide range of industries from energy and defense to the biomedicine and electronics.