A new, nano-coating can repel sludgy shampoo, so that every last, soapy drop slides easily out of the bottle, which could make plastic much easier to recycle.
"Unfortunately, many people do not properly rinse out shampoo bottles before they add them to their recycling. The leftover product in these bottles can cause issues during the recycling process," explained Dr Philip Brown, from The State University of Ohio.
If there's still a few drops of soap left, this can, over time, contaminate the bottle and affect the quality of the recycled material. Another concern is that rinsing recyclables wastes too much water.
Brown and other researchers have now overcome this obstacle by basing their material on an existing plastic called polypropylene - it has a coating of nanoparticles made of silica and quartz embedded at its surface. This new material not only repels the shampoo but stops the contents from touching the sides! The nano-structure of the material forms an air bubble, which holds the soap aloft.
To test it, they put the new material into a liquid. After whirling and heating up the bottle, the nanoparticles burst into the hot plastic and became embedded in it. This formed hooked structures that rise above the plastic surface and, as the plastic cools, it reforms around the nanoparticles and hold them tight. The surface is rough on a microscopic level and creates tiny air pockets which prevent the soap, oil or water from sticking to it.
The repellent effect is further enhanced by treatment with fluorosilane, a chemical that keeps liquid away from the plastic surface. Consequently, the soap doesn't touch the sides of the bottle. Instead, the soap forms droplets and slides easily across the bumpy surface of the bottle, meaning you can easily get every last drop of shampoo and thus make recycling more effective.
This is the first time that a polypropylene surface repels both water and oils at the same time. However, if the liquid is in contact with the surface for a long time, this might decrease its effectiveness. For that reason, Brown is now currently testing if the effects from this nano-makeover last for the entire lifetime of the bottle.
Crucially, his study focused on plastic material, which is these days used by nearly everyone. As a society, we have become dependent on this matter; to the point where it can be challenging to function without it - from computer screens to keyboards - plastic is literally at our fingertips all day long.
This plastic epidemic is taking its toll on the environment as well. Many plastic products are reaching the end of their lifecycle, forming non-biodegradable mountains of waste, and 40% of these come from plastic bottles.
Since resources on the Earth are limited, recycling helps us to reduce not only carbon dioxide emission and oil usage but also the quantities of plastic waste disposal.
While billions of bottles end up in the garbage with product still in them, now, thanks to the prefabricated surface invention, plastics recycling faces less hurdles and maximizes your shower experience.
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