April 13, 2024

Around three billion tires for automobiles were manufactured around the world in 2019. The classic automobile tire is an illustration of a large-scale product made from petroleum resources that are non-renewable and intended for sole use. They are not in line with the design of reduction, reuse, recycle, and reduce.

Old tires are sometimes used for fuel for the industry of cement or crushed into a crumb, which is used to reinforce the structure of the building. Parents are familiar with mats of rubber found in playgrounds for children.

These are unsustainable methods of utilizing an energy source that is not renewable. In the end, many tires are disposed of in landfills, where they could pollute the environment with leakage ( the liquid that is absorbed by landfills and then into the soil) or, even more dangerously, through fires that emit toxic gases and release particulate in the air.

Tire fires

On the evening of Dec. 20th, 2019, a tense fire broke out in the TRACC tire recycling facility located in Minto, N.B., in which approximately 1 million tires were kept. It took about a week to extinguish the flame. These kinds of fires aren’t unusual: Another notable tire fire occurred 30 years ago, and fourteen million tires from Hagersville, Ont., were engulfed in flames for two weeks.

In the early 1840s, Charles Goodyear discovered the process of Vulcanization that transforms soft natural rubber into tough rubbers. Vulcanization utilizes sulfur chains to connect huge organic molecules in networks and continues to be used for the production of automobile tires.

Prior to the advancements in automobile design, including the introduction of radial and steel belts 50 years ago, tires had to be replaced at intervals of between 20,000 and 40,000 kilometers. Today, we expect tires to last for a long time, staying 100,000 kilometers. This reliability when driving makes the tires challenging to reuse.

Innovative ways to degrade tires

In my lab, that of the Brook Research Group at McMaster University, we have developed a highly efficient and simple procedure that utilizes silicone chemistry in order to break the sulfur-sulfur bond that binds tires. The silicones selectively cut off the sulfur-sulfur bonds, leaving organic chains that can be separated and used to make new products. The process was originally developed to create unique silicones by using tiny amounts of a catalyst that has been used to improve the sustainability of petroleum-based tires.

A diagram that shows the steps involved in this process to break up rubber tires. Author has provided

The chemical procedure begins by cutting the tire into sections and then making powdered crumbs from them. These are steps commonly used in tire recycling plants for commercial use. After that, a gentle, fast reaction caused by heating this material with particular silicones in the range of 100C to 45 minutes transforms around 90 percent of organic substances into easily processed light yellow oil. The remainder of the senses, like carbon inorganic silica, silica, iron, as well as polyester cord fibers, are easily removed through filtering.

The oil recovered from tires that have been used are like the polymers that were originally utilized to make new tires. Our lab also shows that they can be recycled.

In one case, the recovered polymers were repurposed into new rubbers, as seen in the above photo of the model tire toy car. The inorganic residue, which was initially removed through filtration, can also be used again to strengthen this new type of rubber.

There is a lot more to be completed. We must better define the types of products that could be created from recycled polymers. We also need to reduce the amount of catalyst required to boost the profitability and efficiency of this process.

The whole process provides a chance to close the loop that automobile tires have created since the rubber can be effectively degraded and recycled to create new materials. It is a fresh approach to make use of the valuable components in tires used for scrap and solve a complex environmental issue.

 

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