A Selective Upcycling Approach: Growing 2D and 3D Graphene Oxide Structures with Size-Controlled Talc Substrates from Waste Polypropylene with LCA Protocols

It is challenging to produce high value-added carbon nanomaterials using a rich hydrocarbon source in thermoplastics with conventional recycling processing techniques which limit their usage. This study demonstrated the growth of sheet-like and spherical graphene oxide structures on talc substrates by providing dissociation of carbon atoms from waste polypropylene (PP) and applying a new upcycling approach by mimicking chemical vapor deposition and supporting with life cycle assessment (LCA) protocols. In the developed process, waste polypropylene was mixed with neat and iron-treated talc templates and then exposed to thermal treatment to provide the deposition of carbon atoms coming from polypropylene waste on the lamellar structure of talc. A selective method to obtain 2D and 3D graphene oxide structures was developed with a suitable talc size and by activating the talc surface, producing different PP blends with talc, and defining suitable pyrolysis and carbonization techniques. Regarding the characterization results, talc size of 12 μm enhanced the growth of graphene oxide nanoplatelets whereas talc size less than 2 μm led to the formation of spherical graphene oxide structures. In addition, a benchmarking study was carried out by this new graphene oxide/talc hybrid additive as a reinforcing agent in PP to develop sustainable and lightweight automotive composites. The incorporation of 5 wt% new hybrid additive into PP enhanced flexural modulus by 88% compared to unfilled PP, and 6 wt% enhancement in flexural modulus and 12% reduction in density are achieved with the new hybrid additive inclusion into PP compared to commercial PP having 15 wt% of talc. LCA study showed 28% CO 2 reduction with the new upcycled graphene oxide structures compared to one produced by chemical exfoliation.