Graphene is a highly desirable material for a variety of applications including nanocomposites, where nano graphene particles are incorporated in a polymer matrix. Nanocomposites have great potential in a range of industries and are already being used in automotive and space applications. Functionalised graphene, where the surface chemistry is altered to change the interaction between the graphene and the polymer material used in the composite, can be added as a nanofiller to change the overall composite properties, such as tensile strength. Often the material properties of the functionalised graphene and the physical location of any additional chemical species are not known. Consequently, there is a limited understanding of why improvements in product performance are achieved, and this hinders the rate of product development.
Versarien Plc develops graphene products and wanted to explore how modifying their material, trademarked Nanene, could change how the flakes are dispersed in a polymer, and in turn, how this would change the mechanical properties. Nanene is a graphitic powder containing few-layer graphene (FLG) flakes and understanding whether improved dispersion of Nanene in polymers will bring added benefits to the composite, would help manufacturers improve their products’ properties. NPL worked with Versarien through the InnovateUK funded Analysis for Innovators programme to understand the chemical and physical processes involved.
NPL applied a wide range of state-of-the-art measurement techniques to characterise the flakes and composites, before and after functionalisation using oxygen- and nitrogen-containing groups. Scanning electron microscopy showed little evidence of changes which would affect the final mechanical properties of the composites. X-ray photoelectron spectroscopy indicated the success of the functionalisation process. Tip enhanced Raman spectroscopy (TERS) provided nanoscale resolution of the graphene’s structural makeup and allowed defects within the flakes themselves to be observed. This was the first nanoscale chemical imaging of commercially-available FLG flakes.
Graphene-polymer nanocomposites were then prepared using graphene with different functionalisation processes and different matrix resins to study dispersion and the impact on the final mechanical properties. This improved the understanding of how the chemical functionalisation was affecting the mechanical properties by correlating the chemical and physical changes on the surface of the FLG flakes.
NPL’s research, in collaboration with the Graphene Engineering Innovation Centre GEIC at the University of Manchester, the University of Liverpool and the University of Surrey, enabled Versarien to understand the effect of functionalised graphene on nanocomposites at a structural and chemical level. The knowledge and data from this collaborative research benefits ongoing product development, and helps provide assurances to new and existing customers. It is also vital in building confidence in new materials so that they move out of the laboratory and into the commercial marketplace.
Dr Andrew Pollard, Science Area Leader at NPL, said: “Understanding how the fundamental material properties of commercially-available powders containing few-layer graphene affect the final performance of real-world products, is crucial if these new and innovative applications are to come to market. It is exciting to see how advanced techniques measuring nanoscale properties can reveal the reasons for changes in the macroscale properties of composites.”
“The outcome of this A4I (InnovateUK) funded project is an excellent example of how metrology enables innovation,” said Robin Wilson, Head of Manufacturing & Materials of InnovateUK. “It has had a far-reaching impact, as it has not only helped a UK company to fine tune their product development but has also resulted in a scientific publication that adds to the understanding of using graphene within the composite community.”
This work has been published in ACS Applied Materials and Interfaces: Determining the Level and Location of Functional Groups on Few-Layer Graphene and Their Effect on the Mechanical Properties of Nanocomposites
Dr Andrew Pollard recently spoke to Chemistry and Industry magazine about this work.