Recycling of PET through the Manufacturing of Carbon Nanofibers

Poly(ethylene terephthalate) is one of the most widely used commodity plastics and the main material for the manufacture of water bottles. Hence, the development of alternative uses of waste PET will have a positive impact on growing environmental concerns.

Our strategy consists of combining recycled PET with lignin for the manufacture of carbon nanofibers. Lignin and PET are miscible and can be blended by dissolving them in the same solvent, as it is demonstrated in our published work. Using the electrospinning technique, the blend is spun into fibrous mats of controllable average fiber diameters in the submicron- or nano-scale. The presence of PET is crucial for the formation of fibers, as lignin alone cannot be electrospun successfully. Finally, the electrospun lignin/PET nanofibers are thermally treated under inert atmosphere at elevated temperatures (>800 ^oC) for transforming them into carbon nanofibers.

Various important features of the carbon fibrous mats, such as the morphology and the porosity, are determined by the average fiber diameter of the precursor electrospun mats, as well as by the relative percentage of PET in the blend. Carbon nanofibers of minimum average diameter (close to 100 nm) can be prepared successfully only when the PET percentage is as low as 10 % w/w. When the percentage of PET is much higher, then it is not feasible to produce carbon nanofibers. However, a higher percentage of PET (around 50 %w/w) leads to much higher microporosity, as the PET disintegrates during carbonization leaving empty molecular space inside the carbon nanofibers.