Fabrication of new oil repellent

Engineers at the Massachusetts Institute of Technology have just designed the first simple process in producing very strong oil-repellent materials. The material can be applied as a complex surface coating and applied in aviation, astronautics and hazardous waste cleaning.

For example, materials that can be used to protect aircraft or missile components are vulnerable to oil seepage, such as small rubber gaskets and rings.

Robert Cohen, a professor of Chemical Engineering and author of a paper about the study, will be published in the December 7 issue of the journal Science. "These are vulnerable parts in applications," he said. space use '.

Cohen said: 'It would be nice if you put oil on a cloth or a pad or on another surface and find that instead of the oil spilling, it will form droplets. Creating a strong oil repellent or oil-repellent material is a challenge for scientists, and no natural material is like this. '

Note: Drops of water form a small bead on the surface of the left lotus leaf (above) , while a liquid hydrocarbon droplet penetrates the leaf surface (top right) . After the lotus leaf was dipped with a new oil-repellent material studied by the Massachusetts Institute of Technology, the water was still in granular form (bottom left) , and so did liquid hydrocarbon (right picture below) .The small picture in the top left frame is the result of a microscopic examination on the surface of the lotus leaf.

Gareth McKinley - engineering professor at the Massachusetts Institute of Technology, Department of Mechanical Engineering and a member of the research team, said: 'Nature has generated a lot of waterproof methods, but for Oil proofing is not much. The law states that this method will not be possible on a large scale without lithography processes'.

Other oils and hydrocarbons tend to overflow on surfaces due to their very low surface pressures (limiting the gravity between molecules in the same substance).

In other words, water has a very large surface pressure and tends to form droplets. For example, water droplets appear on a newly waxed car (however, over a period of time, the oil and grease will contaminate the surface of the car and the water repellency will fade). The difference in surface pressure also explains why water does not form droplets on duck hair, but the oil-dipped duck must be washed with soap to remove the oil.

The Massachusetts Institute of Technology research team has overcome the problem of surface pressure by designing a material consisting of specially prepared microfilm that protects the droplets of solution, making them stand still and intact on the surface of the material .

When oil droplets touch a material similar to a thin fabric or paper towel, they will stay on the fiber fibers and air holes are trapped between fibers. The large contact angle between the oil droplets and the fibers will prevent the solution from sinking to the surface and wetting it.

Microfibers are a combination of special bonding molecules called flouroPOSS , which have extremely low surface pressures, with polymer compounds. They can be built into a variety of surfaces, including metal, glass, plastic and even biological surfaces such as leaves, and these microfilm panels use a known process. come as electroplating printing.

The researchers also developed a number of dimensionless outline parameters that can predict how stable the oil impregnation or osmosis between a certain solution and a surface. These outlined equations are based on structural calculations, namely the concave angle (or concave nature) of surface roughness, and based on other factors such as the surface pressure of the solution. , distance of fiber fibers, and contact angle between solution and flat surface.

By using these connections, researchers can design sheets of fabric that can easily separate different hydrocarbons. They have created a non-bonding fiber that splits water and octane (black material), believing that the fiber could be useful for hazardous waste cleaning.

Air Force - the airline that sponsors the research and invention of fluoroPOSS molecules - is interested in using this new material to protect the components of aircraft and missiles from fuel contamination. black.

The lead author of this study is Anish Tuteja - a doctor who collaborates with the Department of Chemical Technology at the Massachusetts Institute of Technology. Other authors at the Massachusetts Institute of Technology are Wonjae Choi - graduate of the Department of Mechanical Engineering, Minglin Ma - graduate of Chemical Engineering, and Gregory Rutledge, professor of chemical engineering. In addition, Joseph Mabry and Sarah Mazzella at Air Force's research lab are also co-founders of this research.

THANH TAM