Recycling of Mixed Plastics, Foam to Graphene - Rice University

Coverting Scrapped Car Plastic Waste into Graphene

Flash Joule heating process recycles plastic from end-of-life Ford trucks into high-value graphene for new vehicles
The part of an old car that gets turned into graphene could come back as a better part for a new car.

赖斯大学的化学家和研究人员一起工作at the Ford Motor Company are turning plastic parts from “end-of-life” vehicles into graphene via the university’s flash Joule heating process.

The average SUV contains up to 350 kilograms (771 pounds) of plastic

The goal of the project led by Rice chemist James Tour and graduate student and lead author Kevin Wyss was to reuse that graphene to make enhanced polyurethane foam for new vehicles. Tests showed the graphene-infused foam had a 34% increase in tensile strength and a 25% increase in low-frequency noise absorption. That’s with only 0.1% by weight or less of graphene.

And when that new car is old, the foam can be flashed into graphene again.

“Ford sent us 10 pounds of mixed plastic waste from a vehicle shredding facility,” Tour said. “It was muddy and wet. We flashed it, we sent the graphene back to Ford, they put it into new foam composites and it did everything it was supposed to do.

“Then they sent us the new composites and we flashed those and turned them back into graphene,” he said. “It’s a great example of circular recycling.”

Hundreds of different combinations of plastic resin, filler and reinforcements on vehicles make the materials very difficult to separate.Flash Joule heating to make graphene, introduced by the Tour lab in 2020, packs mixed ground plastic and a coke additive (for conductivity) between electrodes in a tube and blasts it with high voltage. The sudden, intense heat -- up to nearly 5,000 degrees Fahrenheit -- vaporizes other elements and leaves behind easy-to-solubilize, turbostratic graphene.

Flash heating offers significant environmental benefits, as the process does not require solvents and uses a minimum of energy to produce graphene.

To test whether end-of-life, mixed plastic could be transformed, the Rice lab ground the shredder “fluff” made of plastic bumpers, gaskets, carpets, mats, seating and door casings from end-of-life F-150 pickup trucks to a fine powder without washing or pre-sorting the components.

The lab flashed the powder in two steps, first under low current and then high current in a heater Wyss custom designed for the experiment.

Powder heated between 10 to 16 seconds in low current produced a highly carbonized plastic accounting for about 30 percent of the initial bulk. The other 70% was outgassed or recovered as hydrocarbon-rich waxes and oils that Wyss suggested could also be recycled.

The carbonized plastic was then subjected to high-current flashing, converting 85% of it into graphene while outgassing hydrogen, oxygen, chlorine, silicon and trace metal impurities.

The Life Cycle Analysis involved comparing graphene from flashed car parts to that produced by other methods, and evaluating recycling efficiency. Their results showed flash Joule heating produced graphene with a substantial reduction in energy, greenhouse gas emissions, and water use when compared to other methods, even including the energy required to reduce the plastic shredder fluff to powder.

Graphene has a future at Ford. The company first introduced it into a variety of other under-the-hood components and in 2020 added a graphene-reinforced engine cover. Kiziltas said the company expects to use it to reinforce hard plastics as well.

Source: Rice University