At best, experiencing a flat tire is an inconvenience. Whether you’re pulling out the jack and lug wrench and changing it yourself or waiting for AAA to come to your rescue, it’s a big waste of time. And in the age of electrification, a new level of tire complexity is emerging. Electric vehicles are heavy, and designers are opting to omit spare tires to save weight. Also, batteries take up a lot of real estate, leaving less room to carry a spare. Overall, tire company Bridgestone says that approximately one-third of all new passenger vehicles sold in the US today are not equipped with a spare tire.
Self-sealing technology can mitigate the issue of an absent spare tire, freeing up space and providing a way to lighten the overall weight of the vehicle, which in turn improves total driving range. Global manufacturer Dow has announced the launch of a recyclable silicone self-sealing tire solution that will allow drivers to travel long distances even after a sharp object (like a nail) punctures the outer wall of a tire. It seals the inner layer to retain tire pressure. No lug nut wrenching required.
Here’s how it works.
Silicone versus other sealants
Giving the driver an opportunity to continue down the road after a puncture offers a major benefit on its own, but what’s more impressive is the sustainability element of silicone sealant, Dow and Bridgestone boast. Bob Lux, Bridgestone Tires’ director for consumer tires, explained to PopSci why silicone is easier to work with than traditional sealants like natural rubber and butyl. An elastomeric polymer used widely in adhesives and sealants, butyl is a synthetic rubber invented in the 1940s. It has been effectively used as a sealant for many years, but companies like Bridgestone are finding that it has a host of challenges that can be solved with silicone.
“Manufacturers are starting to apply sealant more widely,” Lux says. “It’s not necessarily new as they have been around in some form since the 90s, but it’s much better today because silicone sealant doesn’t cause ride disturbances. In the past, sealants didn’t stay in place and would shift and cause unevenness. Today’s sealants don’t cause that issue.”
Unlike aftermarket sealants like Fix-a-Flat, which are sold in single-use cans, this silicone sealant is applied to the tire for preemptive protection during the manufacturing process. This seals the puncture wound to maintain tire pressure like a superhero absorbs and instantly heals from epic battles on screen.
Sustainable tire practices
From an energy-saving standpoint, silicone is also easier to employ because it’s applied at room temperature. Natural rubber and butyl require heat from the preconditioning phase to application, and heat consumes more energy. Previous sealant materials are sticky, too, which causes a significant problem in the recycling process. Tires are chopped up and recycled in a number of ways to use in roads, as playground material, or back into the tire manufacturing cycle.
“At the end of life for a tire, recycling becomes very difficult with traditional sealant inside,” Lux says. “[Traditional] sealant will gum up the machines that chop up tires for recycling.”
Not silicone, however. Using this kind of new sealant technology could result in a reduction of the number of tires in the landfill, although the silicone needs to be removed first. Then the silicone itself can be recycled separately and used as an industrial lubricant, playground mulch, and more.
Run flats or sealant?
Speaking of getting a flat, you may have heard of run-flat tires. They have been growing in popularity in recent years, thanks to their convenience factor. Companies like Bridgestone and BFGoodrich manufacture run-flats, which employ reinforced sidewalls to give drivers a way to limp to a safer place to change it out.
Meanwhile, the repairable area of a tire is approximately a quarter-inch in case of a puncture, and sealant holds the tire together. Basically, run-flats can help in the case of difficult sidewall punctures, while sealant protects the tread area.
Theoretically, silicone sealant could be paired with run-flats for extra protection, but that combination isn’t a priority for EVs currently. “We see a big impact on range with silicone sealant,” Lux says. “It’s lighter and doesn’t impact rolling resistance.”
Bridgestone will be adding this co-developed sealant into tires for a car manufacturer fitment soon; Lux says it will be released in 2023.