Urethane Recycling

November 11, 2005 | Skip To The Comments (1)

Urethane Recycling: Examining what is and isn't done with wheels
By Rob Brink
TransWorld Skateboarding Business January 2003

“That's going to be a short article isn't it?”

—George Powell

You would assume that with all the technological advancements in this world, finding ways to recycle all of the materials we use to make our lives fun and exciting would be a cinch.

Colonizing Mars is just on the horizon, but finding a way to reuse urethane waste from the manufacturing of skateboard wheels isn't "practical" or "cost-effective."

The majority of wheel waste is generated in the wheel-shaping process—essentially a lathing down of the already-cast wheel. Before the early 90s, urethane manufacturers molded wheels to their final shape, and a cut was made on the back to make it match the front of the wheel. This generated some, but not much, scrap urethane. But as things progressed into the 90s, the marketplace demanded more custom-shaped wheels. So with the desire to have different shapes, the urethane manufacturers ended up cutting wheels on all sides, generating twice the amount of scrap they had before. "This is where, if we could recycle, it would be nice," says John Tiedeman, vice president of Creative Urethane. "It's doable, but not economically feasible."

What makes recycling urethane so expensive? Well, put simply, it's the fact that the components of the wheel are chemically bonded together, making them very difficult and very expensive to separate—or even just change their form. Urethane is a thermoset material, which means that once it is formed and reacted, it stays that way forever—unlike a thermoplastic such as nylon that can be reformed having most, if not all of its original properties.

One application for urethane waste is similar to Nike's regrinding program that takes old shoe soles, grinds them up, and uses them as artificial turf or playground surfacing. The dilemma lies in the fact that the action of grinding the urethane causes heat, which causes urethane to melt, and it ruins the machines that grind it. So it isn't practical to use the "regrind" method. Tiedeman explains: "You could freeze the urethane with liquid nitrogen to keep the temperature down, and it would grind like a regular plastic and not ruin the machinery, but again that comes back to the fact that to fund the equipment to do it would cost a lot of money."

It seems that because breaking down and reusing urethane is too expensive, there must be ways to reuse the already-formed urethane and somehow keep the amounts going to the landfills to a minimum. "We'd love to be able to recycle," says George Powell, "but the leftover stuff basically gets reacted in a drum and sent to the dump. Wheels that are no good we cut in two and throw in the dumpster." But Powell explains it's not from a lack of trying: "We've looked for years because we hate to throw away material that we spend a lot of money on per pound, but the only thing we've been successful with as far as recycling urethane has been giving our wheel trimmings to local art groups. They make decorative things out of them.

In the late 90s, Tiedeman stumbled across another use for urethane shavings (a use that only scientists like Tiedeman could discover). It's a methodology for creating a surface area for biomass generation in fish tanks. The biomass are tiny organisms that generate oxygen, and the lathings from the wheels create thousands of feet of twirly-piece urethane surface area for the biomass to live on. Once the urethane is placed in the water, it doesn't float and it doesn't sink, but it's within the entire volume of the water—it has almost the same density as water. So the biomass grows very well and with all the surface area it was really good for them. However, when the fish tanks are cleaned, the water is filtered and the biomass is shaken off to clean it. The urethane doesn't go away and it never gets used up, so they never need more of it, then it is put back in the water—a one-time application. “I fitted everyone in the local area with this stuff, and that was three years ago. If someone had the inclination to go search for the customers, we could supply the world with biomass surfacing,” said Tiedeman jokingly, who also spoke with a major supplier of raw materials for polyurethane businesses, mentioning to them that it was their responsibility to get the ball rolling on recycling these materials, because there is a lot of urethane being used in the world. “They said they are working on it, so there may be a time in the near future where it may be more economical to start doing that.”

George Powell adds, “We could recycle everything if we just made injection molded wheels. Of course no one would like them.” The injection-molded process involves heating and melting the solid urethane, and then injecting it under pressure into the mold. It is then rapidly cooled and removed from the mold. It's really just a reforming of shape—like water into ice. However, heat from the bearings will want to reform the material, enlarging the bearing seats over time. Powell continues, “It's kind of like, you make stuff that's really good but, because it is so good it isn't recyclable. It's a function of it not being a thermoplastic. That's why it's stronger and has better abrasion resistance and all the stuff you want. But it's all bound together chemically and that's what makes it work.”

Bryan Hanson, sales rep for Creative gives wheels to his friends who in turn give them to their dogs as chew toys. “They can't chew them up and they are too big for the dogs to swallow,” says Hanson. So until technology catches up, and the costs of urethane recycling goes down, we must be comforted my the fact that urethane waste is miniscule compared to that of say, plastic soda bottles, and that the big manufacturers do have the environment in mind—it may just take some time. So for now, let's just find more fish tank people, elementary school art students, and people with dogs, and skaters who don't mind small, hand-me-down, worn out, yellow wheels to help keep the landfills urethane-free.

1 comment

  1. Interesting article which helps to explain my reluctance to mix urethane with rubber for playground surfaces and then promote it as an environmental benfit by recycling tires when it will still end up in a landfill. What does it realy matter if it takes place now or twenty years later to get there?

    David Verbeck

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