Upcycling end-of-life vehicle waste plastic into flash graphene

Responsible disposal of vehicles at the end of life is a pressing environmental concern. In particular, waste plastic forms the largest proportion of non-recycled waste material from light-duty vehicles, and often ends up in a landfill. Here we report the upcycling of depolluted, dismantled and shredded end-of-life waste plastic into flash graphene using flash Joule heating. The synthetic process requires no separation or sorting of plastics and uses no solvents or water. We demonstrate the practical value of the graphene as a re-inforcing agent in automotive polyurethane foam composite, where its introduction leads to improved tensile strength and low frequency noise absorption properties. We demonstrate process continuity by upcycling the resulting foam composite back into equal-quality flash graphene. A prospective cradle-to-gate life cycle assessment suggests that our method may afford lower cumulative energy demand and water use, and a decrease in global warming potential compared to traditional graphene synthesis methods.

2. All connections, wires and components must be suitable for the high voltages and currents.
3. Be aware that component failure could cause high voltage to appear in unexpected places, such as heat sinks on the switching transistors.4. Control wires should have opto-isolators rated for high voltage.
5. Provide a visible charge indicator.A 230 V clear glass incandescent light bulb is a good choice as the glow on the filament also provides an approximate indicator of the amount of charge on the capacitor bank.Bright light = danger!6. Do not use toggle switches with metal toggles.If an arc develops, the metal toggle could become charged.Use only properly rated circuit breakers.7. One hand rule.Use only one hand when working on the system, with the other hand not touching any grounded surface.8. Install bleed resistors in the range of 100,000 ohms on each capacitor so that charge will always bleed off in ~1 h. 9. Provide a mechanical discharge circuit breaker switch connected to a power resistor of a few hundred ohms to rapidly bleed off the capacitor charge.10.Provide a "kill" circuit breaker switch to disconnect the sample holder from the capacitor bank.11.Provide an AC disconnect circuit breaker switch.
12. Post high voltage warning signs on the apparatus.
13. Use of circuit breakers as switches.Circuit breakers have built-in arc suppression that can interrupt 1000 amps or more.Conventional switches do not have such a high level of arc suppression and can burn out or weld closed due to the high current pulses.
14. Use circuit breakers rated for DC voltage.Most AC circuit breakers have a DC rating ½ the voltage or less, since DC arcs are much more difficult to suppress.Circuit breakers designed for DC solar power systems are a good choice.
15.When choosing circuit breakers, choose by the time curves typical for 0.1 s, rather than the steady state current rating.K-type DC circuit breakers will have ~10x higher trip current at 0.1 s compared to their rated current, and Z-type breakers will have ~4x higher trip current at 0.1 s.This "delayed trip" designed into most circuit breakers will allow much higher pulse currents than the steady state rating of the breaker.
16. Include a small amount of inductance in the discharge circuit to limit the rise time to a millisecond or more.Extremely fast discharges can damage components and cause RF interference with other lab apparatii.17.Keep in mind that the system can discharge many thousands of Joules in milliseconds, which can cause components such as relays or even capacitors to explode.These components should be enclosed to protect against both high voltage and possible flying debris.
18. Keep a voltmeter with high voltage test leads handy at all times.When working on the capacitor bank, always check the voltage on each.A broken wire or loose connection could leave the capacitor in a charged state.
19. Wear thick rubber gloves when using the apparatus to protect from electrocution.As the solvent is able to recovered after centrifugation, the majority of surfactant will be recovered after centrifugation.However, significant amounts of surfactant will be bound to the graphene sheets as well as lost during the centrifugation and rinse process, assumed here to be 3%.

Supplementary Figure 2 :
20.All users should be properly trained by an experienced electrical technician.21.Welder's glasses should be worn to minimize eye damage risk by the bright emitted light resulting from the flash (IR and visible photons can cause eye damage).TGA of ELV-WP, carbonized ELV-WP (after LC step), and ELV-WP- Due to the volume and identity of chemical waste streams produced, from the strong oxidizing agents and reducing agents, it is not surprising that consideration of waste streams greatly increased their reported CED.Concerning the results disclosed in the 2014 Arvidsson publication, they determine that sonication uses 470 MJ kg -1 of graphene solution synthesized.However, their LCA has some key differences and is therefore difficult to directly compare to our findings.First, their functional unit for the study is 1 kg of graphene in solution, whereas our functional unit is 1 kg of graphene powder.Most noticeably, at no point in the 20 μm for the graphite precursor is required byZhamuet al., but no graphite milling step is discussed by Arvidsson et al.Further, in their sensitivity analysis, they demonstrate that assumption of solvent recovery can greatly improve the calculated CED and environmental impacts.However, at no point does Arvidsson et al. discuss how they would recover the solvent, or how this recovery process would impact the CED.Lastly, no Raman spectroscopy is given to S15 characterize the quality of, or even confirm the presence of, graphene produced through this surfactant-free sonication technique reported by Zhamu et al.The LCA by Arvidsson et al. on the sonication production of graphene, based off of the disclosure of Zhamu et al. serves to underscorethe extremely wide range of approaches and strategies that currently exist in the graphene production industry.Increased understanding of the graphene production process by increasing process transparency and industrial standardization will hopefully result in more test cases, and more detailed and accurate LCA to be carried out as graphene becomes more widespread.
Supplementary Table 2:A comparison of CED data from recent LCAs of graphene synthetic methods.SupplementalDiscussion of the LCA CED Values.As shown in Supplementary Table 2, the CED values from this study generally agree well with LCAs that have previously been done.The clear outliers are the FJH method (discussed in detail in the manuscript), the study by Serrano-Lujan et al. in 2019, and the study on sonication by Arvidsson et al. in 2014.The Serrano-Lujan study includes disposal and waste stream management as well as some production stream infrastructure/hardware. manuscript is the assumed amount of solvent needed or assumed graphene dispersion concentration disclosed, and no surfactant is used.It is well-documented that pristine graphene concentrations in solvent systems with no surfactant are extremely low (see: Y Hernandez et al.,where they reported concentrations of 0.01 mg mL -1 ).7Despite this, Arvidsson et al. use diethyl ether with no surfactant as the sonication media in their LCA, citing a patent by Zhamu et al.8Zhamu et al. assert that graphene concentrations between 1 mg mL -1 and 10 mg mL -1 can be reached in these surfactant-free polar solvent systems, yet no data supporting this claim (such as UV-Vis absorption or solution phase Raman spectroscopy) is given in the patent, and to our knowledge no literature exists supporting these claims.Further, assuming that such high concentrations are indeed able to be achieved during sonication, it is unclear how the graphene will not re-aggregate to graphite in the solvent system following sonication.Further, a beginning grain size of

Table 3c .
Contributions, notes, and sources resulting from the rinsing, filtering, and drying portions of physical exfoliation.The grand totals are also shown.