Carbon Nanofibers from a Blend of Lignin with Recycled PET: Properties and Characterization

Abstract

Carbon nanofibers are a high value-added form of carbon, which carry an array of remarkable properties. Their high specific surface area and tunable porosity, together with high thermal stability, superior tensile strength and relatively easy manufacturing route has rendered them appropriate for a variety of large-scale applications, such as for adsorption, catalysis, energy storage and as fillers for polymer-based nanocomposites. Primarily they are commercially manufactured through the spinning and the thermal treatment of suitable polymeric precursors, mainly poly(acrylonitrile). However, the relatively high cost of this precursor has triggered the investigation of alternative inexpensive and/or renewable raw materials. In this context, a promising potential is exhibited by lignin, the second most abundant natural polymer behind cellulose. Its suitability is based on its relatively high-carbon content, on its large availability and on its low price. In addition, poly(ethylene terephthalate) (PET) is one of the most widely-used commodity polymers and the most widely recycled plastic in the USA in terms of weight. Hence, alternative uses of recycled PET will have a positive environmental impact.

In this study, lignin was blended with recycled PET and it was spun into precursor nanofibers via the technique of electrospinning. Following a design-of-experiments statistical methodology, the process was optimized and the fiber diameter was minimized. The precursor nanofibers were then carbonized into carbon nanofibers and were activated. Here, we report the results of the characterization of the carbon nanofibers, focusing on the effect of the nanoscale diameter and of the lignin weight ratio on the carbonization process, their specific surface area and the carbon structure. These results can be utilized for the preparation of tailor-made carbon nanofibers of desirable properties focused on a specific application.