This Small Business Innovation Research Phase I project strives to control the chemical properties and the morphological structure of a polymer nano-composite surface, at scales ranging from nanometers to the macroscopic, to achieve superhydrophobic and icephobic properties while exhibiting scratch and abrasion resistance. The goal is to apply this knowledge to manufacture superhydrophobic and icephobic surfaces over large areas and at low cost for commercial and defense applications. Materials design of nano-micro-macro scale surface features will be guided by experimental and model-based analysis to optimize the wetting and mechanical durability of the surfaces. This project's contributions to polymer science would include a fundamental understanding of the relationship between polymer structure, molecular weight and viscosity on the formation of nanocomposite materials with a specific structure, as well as optimization of a processing route to achieve a desired surface morphology. Contributions to surface science would include an understanding of the impact of surface morphology over several different length scales on the wetting behavior of liquid water as well as super-cooled water droplets.
The broader impact/commercial potential of this project would be improvements in the safety of food handling equipment, as well as the performance and reliability of outdoor infrastructure that is subject to icing conditions, such as stadium roofs, wind turbines, aircraft, and naval structures. Equipment used to wash food can harbor bacterial in areas that retain water. By applying a scratch- and abrasion-resistant superhydrophobic surface, safety would be significantly improved, as the potential for water to be harbored in reservoirs would be greatly reduced. Surfaces that repel super-cooled water could be used outdoors to prevent the formation and accretion of ice layers. In this way the safety of numerous structures could be improved, as the added weight of ice accumulation would be avoided. For example, these surfaces could be used to prevent the accumulation of ice on aircraft surfaces. Avoiding the build-up of relatively small amounts of ice can provide a significant margin of safety, because the impact of icing on airflow patterns, rather than the added weight, is the cause of icing-related aircraft accidents. The mechanical durability of the surface would insure that the superhydrophobic properties are retained for many years even when exposed to rough handling conditions.
Submitted by: ARL Designs LLC Superhydrophobic (i.e. highly water repellant) surfaces provide properties desired by industry such as self-cleaning, anti-icing, drag reduction and retarding of bacteria growth. However, superhydrophobic surfaces can be delicate, expensive and difficult to scale up for production. SBIR 1215288 Phase I research demonstrated a break-through fabrication technology allowing us to produce superhydrophobic surfaces on free standing polymer films that are mechanically robust, chemically stable and readily scalable using commercially available materials and equipment. Superhydrophobic surfaces over 10 SF in size were produced with high density polyethylene (HDPE) and thermoplastic polyolefin sheeting as well as with woven and nonwoven fabrics. Samples were shown to possess excellent abrasion resistance under soft and hard abrasion conditions as well as scratch testing and measurements of ice buildup. In addition, initial accelerated UV tests demonstrated the stability of the superhydrophobic properties when the initial polymer incorporated UV stabilizers. Treated HDPE surfaces could also completely prevent ice accretion from 0oC water droplets when surfaces were cooled to -20oC. In this study, we systematically studied the effects of process conditions, including sheet feeding speed, on the performance of the treated surface since production speeds will largely determine the economics of the technology. Results were encouraging and further scale up is planned.
