Crumb rubber is derived from end-of-life tires and is the smallest and highest end use of recycled rubber. Crumb ranges in size from incredibly small particles that are almost dust-like, to roughly a ½” in size. Most of the crumb rubber used in the world is known as 10:20 mesh, which is about the size of a particle of sand.
As an aside, mesh size is used as a descriptor and designates how many holes per square inch in the screens used for sizing. A 10:20 product means there are 10 holes on the top screen and 20 holes on the bottom screen, both per square inch. The material in that setup would produce 10:20 mesh which is all the material captured in the middle between the two screens.
Crumb rubber can come from a variety of types of tires but for this discussion let’s look at crumb rubber made from tires like one’s on your vehicle. When a tire is recycled more than just rubber is reclaimed from a vehicle tire. Vehicle tires have steel belts and fiber used to reinforce the tire and give it greater longevity on the road. Both components are recycled into other products and uses as well.
As the tires go through the grinding process into smaller and smaller pieces, steel and fiber is removed during the process. This is called ambient grinding. The smaller the rubber particle, the more steel and fiber is removed and given a second life. But grinding a tire is not the only way to break the tire down into crumb rubber.
Cryogenic processing is a process where rubber is frozen and then shattered into small pieces which is higher tech than ambient grinding. This process uses liquid nitrogen to freeze the rubber particles before turning them into smaller pieces. Once the rubber is frozen below -80 degrees Celsius the rubber becomes very brittle. At this stage in the process, it goes through what is called a hammermill that smashes the larger rubber pieces into smaller ones.
Next time you purchase something that is either made from rubber or has a rubber component take a moment to think…is this made from the same tires that I drove to work on every day for the past four to five years? It just may be…it just may be…