Ford Motor Company is collaborating with Rice University to process the plastic parts of used vehicles to produce graphene. The carmaker sells more than 3.5 million units every year.
The average SUV contains up to 350kg of plastic and much of the mixed plastic ends up being incinerated when the car is scrapped, according to Deborah Mielewski, technical fellow for sustainability at Ford. She points out that the US shreds 10 to 15 million vehicles each year, with more than 27 million shredded globally.
But there is an alternative, according to Rice University chemist James Tour and graduate student Kevin Wyss. They report that automotive parts can be ground into powder and converted into graphene thanks to the University lab’s innovative flash Joule heating process.
The R&D project was established to create enhanced polyurethane foam for new vehicles. Tests showed that 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,’ says Wyss.
Ford sent the lab team 5kg samples of mixed plastic waste from vehicle shredding facilities to work with. ‘The material was muddy and wet,’ Tour recalls. Once Ford realised the recycled material ‘did everything it was supposed to do’, the lab started working on production waste composites – again with promising results.
How does it work?
Mixed ground plastic and a coke additive (for conductivity) are packed between electrodes in a tube and blasted with high voltage. The sudden intense heat – upwards of 2 700° Celsius – vaporises other elements and leaves behind turbostratic graphene.
Flash heating offers significant environmental benefits as the process does not require solvents and uses a minimum of energy to produce the graphene.
To test whether end-of-life, mixed plastic could be transformed, the Rice lab ground the shredder ‘fluff’ from bumpers, gaskets, carpets, mats, seating and door casings from end-of-life F-150 pickup trucks into a fine powder without washing or pre-sorting the components.
The lab flashed the powder in two steps, first under a low current and then a high current in a heater Wyss designed for the experiment. Powder heated between 10 to 16 seconds in low current produced a highly carbonised plastic accounting for about 30% of the initial bulk. The other 70% was either dispersed as gas or recovered as hydrocarbon-rich waxes and oils.
The carbonised plastic was then subjected to high-current flashing, converting 85% of it into graphene while shedding hydrogen, oxygen, chlorine, silicon and trace metal impurities.