Development and Stabilization of Hybrid Structure of Asphaltene and Graphene

Petroleum and its derivatives, such as bitumen, are complex colloidal system. Their chemical behavior is influenced by various internal and external factors. Adding graphene derivatives to this system will only increase its complexity, thus it must be carefully considered to ensure successful integration. In this thesis, we examine the challenges of introducing graphene derivatives into bitumen and focus on three key questions: a) phase stability of graphene derivatives in bitumen, b) interaction between graphene and asphaltene aggregates, and c) an environmentally friendly and optimal method to modify graphene derivatives for improved bitumen properties. We use various characterization techniques to answer these questions and find that the best strategy for introducing graphene derivatives into bitumen is non-covalently functionalized graphene using the Molecular Wedging method (MW-graphene). The MW-graphene is compatible with asphaltene aggregates and stabilizes in bitumen through mutual interaction. The use of MW-graphene improves the mechanical stability of asphaltene aggregates in bitumen

Interaction Between Graphene Derivatives and Asphaltenes in Crude Oil and Crude Derivatives

The chemistry of crude oil (SARA) and crude derivatives, and the percentage of asphaltene can vary significantly depending on external and internal factors such as the source and method of SARA extraction. If graphitic materials are introduced into a system such as SARA, it becomes an additional variable to a complex multi-phase colloid. Within the framework of this thesis, we focus on the phase stability and particle interaction between graphene and asphaltene in order to optimise the process of tailoring the microstructure of graphene embedded SARA systems, such as bitumen, to improve the gas barrier and thermal conductivity. We use various characterisation techniques in this thesis to observe the phase behaviour and the impact of embedding graphene derivatives such as GO to crude derivatives. Phase separation and agglomeration, within the SARA subfractions, were the main focus. The observations and results from the studies prove that GO is detrimental to the structure and functioning of SARA. After this observation, we attempted and succeeded in producing an fGO, that was able to overcome the challenges put forth by GO. The fGO formed stable structures, with other molecules in SARA

Influence of Graphene Oxide on Asphaltene Nanoaggregates

Asphaltenes are a group of exotic hydrocarbons found in bitumen and other forms of heavy crude oil derivatives. These hydrocarbons, with elusive chemistry, give crude oil derivatives (CODs), such as bitumen, its characteristic properties. In bitumen, they form stable aggregates by interacting with other molecules, called asphaltene aggregates. Attempts have been made to enhance bitumen with nanoparticles, like graphene derivatives. Such studies have been successful in displaying the enhanceability of bitumen, but no studies have been directly focused on how the structural stability of asphaltene aggregates present in bitumen is affected by the incorporation of nanoparticles. The phase stability of the asphaltene aggregates is a pertinent question, which is often ignored. In this study, we investigate the physical impact of incorporating graphitic nanoparticles on the structure of bitumen. For this, we utilise graphene oxide (GO). GO is a form of polyaromatic nanoparticle with a similar structure to asphaltenes, such that both have molecular defects induced by heteroatoms. We have experimentally investigated the structural stability of the asphaltenes, using XPS, XRD and SEM-EDX to elucidate the interaction between asphaltenes and GO, and its implications for the stability of bitumen used for e.g., the surface layer of roads. In roads, asphaltene aggregates exist as stable structures, until GO has been introduced. The experimental results show that the introduction of GO initiates destabilisation of the asphaltene aggregates, and we discuss the destabilisation mechanism in this paper. Thereby, we conclude that counter intuitively, the introduction of graphene or GO has a negative impact on the structure of bitumen, thus hindering any functional enhancements to bituminous roads

The Critical Role of Asphaltene Nanoaggregates in Stabilizing Functionalized Graphene in Crude Oil Derivatives

Graphene derivatives have been seen as an additive to improve the material properties of bitumen, such as thermal conductivity, viscoelasticity, and mechanical strength. However, in our previous work, a critical challenge was identified. When graphene derivatives are incorporated into bitumen, it leads to detrimental effects. This is due to the poor phase compatibility of graphene derivatives with asphaltene aggregates, the intrinsic aggregates that give bitumen its characteristic properties. In this work, we focus on tailoring the surface chemistry of graphene, thorough non-covalent functionalization, to achieve phase compatibility with asphaltene aggregates. In addition, the work also focuses on stabilizing this functionalized graphene in bitumen. To achieve this, the graphene was functionalized with -COOH tethers by the Molecular wedging method. Thereafter, the same molecules that form the asphaltene aggregates were used to stabilize the functionalized graphene by embedding the -COOH tethers in the asphaltene aggregates. As a result, graphene functionalized by this strategy was observed to be stable in bitumen and phase compatible with asphaltene aggregates. Thus, a successful environment-friendly strategy was developed to utilize the potential of graphene to improve the material properties of bitumen

Linear and Nonlinear Rheology Combined with Dielectric Spectroscopy of Hybrid Polymer Nanocomposites for Semiconductive Applications

The linear and nonlinear oscillatory shear, extensional and combined rheology-dielectric spectroscopy of hybrid polymer nanocomposites for semiconductive applications were investigated in this study. The main focus was the influence of processing conditions on percolated poly(ethylene-butyl acrylate) (EBA) nanocomposite hybrids containing graphite nanoplatelets (GnP) and carbon black (CB). The rheological response of the samples was interpreted in terms of dispersion properties, filler distortion from processing, filler percolation, as well as the filler orientation and distribution dynamics inside the matrix. Evidence of the influence of dispersion properties was found in linear viscoelastic dynamic frequency sweeps, while the percolation of the nanocomposites was detected in nonlinearities developed in dynamic strain sweeps. Using extensional rheology, hybrid samples with better dispersion properties lead to a more pronounced strain hardening behavior, while samples with a higher volume percentage of fillers caused a drastic reduction in strain hardening. The rheo-dielectric time-dependent response showed that in the case of nanocomposites containing only GnP, the orientation dynamics leads to non-conductive samples. However, in the case of hybrids, the orientation of the GnP could be offset by the dispersing of the CB to bridge the nanoplatelets. The results were interpreted in the framework of a dual PE-BA model, where the fillers would be concentrated mainly in the BA regions. Furthermore, better dispersed hybrids obtained using mixing screws at the expense of filler distortion via extrusion processing history were emphasized through the rheo-dielectric tests