Friday, April 19, 2024

Turning plastic parts from end-of-life vehicles into graphene

Due to decreasing cost of entry and an increasing global standard of living, automobile access has expanded ownership to record highs. When these vehicles come to the end of their useful life they end up as discarded vehicles.

Rice University chemists working with researchers 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 of plastic that could sit in a landfill for centuries if not for a recycling process outlined in a new study published in the debut issue of a new Nature journal, Communications Engineering.

The project, led by Rice chemist James Tour and graduate student and lead author Kevin Wyss, focused on reusing graphene in old cars to make enhanced polyurethane foam for new vehicles. Their tests showed that 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. Importantly, when that new car is old, the foam can be flashed into graphene again.

Introduced in 2020, the flash Joule heating to make graphene 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. In addition, the flash heating process offers significant environmental benefits since it does not require solvents and uses a minimum of energy to produce graphene.

Rice lab tested its process by grounding 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 team then flashed the powder in two steps, first under low current and then high current in a heater.

They found powder heated between 10 to 16 seconds in low current produced a highly carbonized plastic accounting for about 30% of the initial bulk. The other 70% was outgassed or recovered as hydrocarbon-rich waxes and oils. 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.

Ford has been using up to 60 pounds of polyurethane foam in its vehicles, with about 2 pounds of that being graphene-reinforced since 2018, according to co-author Alper Kiziltas, a technical expert at Ford research. “When we got the graphene back from Rice, we incorporated it into our foam in very small quantities and saw significant improvement,” he said. “It exceeded our expectations in providing both excellent mechanical and physical properties for our applications.”