- Retread is a sustainable re-manufacturing process that applies new tread to worn tires.
- A retreaded tire takes 20% of the energy used to create a brand new tire.
- Watch machines from international group Marangoni retread industrial tires.
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The disposal of tires represents a significant burden on the environment, so companies like Marangoni developed methods to recycle and reuse old tires. Watch how retreading machines make old tires usable again.
Following is a transcript of the video.
Narrator: When your tire wears out, you take it to a shop where it's tossed out for a new one. The discarded tire is typically recycled — ground up and chemically broken down to use as a building material in streets or parks. Some companies hope to recycle differently. For years, companies like Marangoni have been saving tire casings, replacing the old tread (the rubber that touches the ground) with new tread in a process called "retreading." These tires are not only easier to make — they typically take 20% of the energy of creating a new tire — they perform well too, standing up to the same tests that one-use tires are subjected to.
The main advantage of the tire-retreading process comes from reusing the casings, which accounts for about two-thirds of the value of a new tire. Reusing tires also cuts down on the amount of raw material used and CO2 emitted during the industrial production process.
Let's take a look at the retreading process step-by-step.
A worn tire that is to be retreaded comes into the factory and undergoes visual and instrumental checks. Integral to this step is a Laser Shearography device, a tool that scans the tire in a vacuum to detect damage or defects not visible from the outside as well as separation of the plies, the group of cords and metal wires within the tire. Tires unsuitable for retreading are not discarded, they are destroyed in a thermal processing plant that burns the tires in an enclosed furnace, converting the tires into usable energy without an enclosed furnace, converting the tires into usable energy without emitting harmful gases. The unburned material is recovered. Casings deemed suitable for retreading are tagged with a barcode and are ready to be buffed.
Casings enter a machine that buffs off the remaining tread. The amount of tread that's removed varies according to the type and size of the casing. The surface is now ready for the application of the new tread.
The buffed casing moves to the crater processing stage. Here it is inspected, and any surface imperfections are repaired. The buffed tire is coated with a sticky layer of non-vulcanized rubber or gum. A pre-vulcanized ring tread liner is stretched and fitted around the tire. A laser ensures the machine is centered on the tire, while clamps emerge and press the tread liner down. The machine holding the tread withdraws. Rollers emerge and smooth the tread liner to the casing.
Each tire is fitted with a rubber envelope and vacuum-sealed. They are brought to an autoclave, or pressure chamber, where each tire will be cured. The tires are simultaneously subjected to immense heat and pressure. The chamber heats up to 250° F and imposes around 88 pounds of force per square inch for two and a half to three hours.
Finally, a technician applies the finishing touches.
EDITOR'S NOTE: This video was originally published in March 2019.
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