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China researchers discover method for recycling silicone

A cheaper, more efficient way to recycle silicone into solar panels

Americans love sex toys—we spend $15 billion on them every year. But when we're done using them, we don't have much recourse other than to dump them into landfills. Fortunately, researchers in China have developed a new technique for recycling silicone, the rubbery plastic substance used in an increasingly large number of bedroom playthings.

Silicone is a compound with organic and inorganic components; its "backbone" of silicon and oxygen is found in common sandstone, but the other compounds they are mixed with are man-made.

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The resulting product is very chemically stable, not very reactive to other chemicals or temperatures, and is difficult for other things to stick or bind to. It's waterproof, hypoallergenic, and doesn't transmit unwanted chemicals to human bodies. It also doesn't decompose, ever. It's therefore used in many applications from cookware and sealing caulk, to cosmetic microbeads and breast implants.

Sex toys at a store in Moscow. Image: Pavel L Photo and Video/Shutterstock

Scientists already have techniques for recycling silicone, but they're expensive. That's because it is very energy-intensive to strip the substance down.

"At present, the 'green' method to reuse the waste silicone is that some companies collect discarded silicone products and smash them for other low-value applications," Lie Shen, a professor of polymer science and engineering at Zhejiang University in Hangzhou, China and one of the study's authors, wrote in an email.

Some types of low-grade silicone can be broken down to their chemical components and reused, he added, "but the methods are of high cost and processes are complicated."

The new recycling process is less energy-intensive and puts the super-water-resistant product to practical use, notably as insulation and as a component of self-cleaning glass.

It's also surprisingly simple. In the  study, published this month in the journal RSC Advances, researchers took a piece of processed silicone—like what you would find around the house on a cupholder or non-stick pan—and cut it into smaller pieces. They then "held [the pieces] in the flame of alcohol lamp in the air until the silicone pieces were completely burned," the study reads, like the researchers were roasting marshmallows around a campfire. Once the silicone was sufficiently charred, they used a hot press to compress it into a solid or pulverize it into a powder.

The result is a substance with a coarse, durable surface that is very water-resistant because the honeycomb-like nanostructures trap air that doesn't let water near the surface itself. The researchers even tested its durability with sandpaper and found that it held up surprisingly well, though not perfectly. These are features that scientists have been trying to develop for a long time, drawing inspiration from water-resistant natural materials like lotus leaves and spider silk.

Highly durable, rubbery materials like these are useful for insulating high-voltage outdoor electrical facilities, like solar panels. The powdered form is also water-resistant and can withstand a number of conditions and temperatures, which makes it useful when incorporated in self-cleaning glass, or the coating that can be used on the outside of the solar panels themselves.

By making solar panel components cheaper and easier to obtain, Shen and his team may have found another small way to make solar energy just a little more viable. At the very least, you'll know what will happen to your old silicone-coated vibrator when you decide to finally treat yourself to the Rabbit.