Self-healing conducting composite electrodes derived from chemical recycling of PET plastic wastes for flexible supercapacitors

As societal advancements and living standards rise, the consumption of polyethylene terephthalate (PET) beverage bottles is witnessing a sharp increase. However, the haphazard disposal of PET-containing products leads to environmental degradation and loss of valuable resources. The development of economically viable methods for recycling waste PET is of paramount societal significance. Thus, we developed a conductive polymer composite through an innovative strategy rooted in self-healing polyurethane (PU) derived from chemically recycled components of waste PET plastic. Through the glycolysis of PET with ethylene glycol (EG), we obtained a high yield of 97.1% of a pristine recycled feedstock known as bis(2-hydroxyethyl) terephthalate (BHET), renowned for its distinctive functional groups and abundant hydrogen bond stacking domains. Leveraging these attributes, monomers of recycled BHET (r-BHET) were used as building blocks for synthesizing high-performance PU elastomers with good mechanical properties, high thermal stability, and remarkable self-healing capabilities of the polymer matrix. By synergistically combining recycled BHET-based self-healing PU with an optimized hybrid carbon nanofiller content, we developed healing composites that exhibit high conductivity (>8.20 × 10² S m⁻¹). These composites are ideal for use as supporting electrodes in flexible supercapacitor devices. The resulting device retains 94.3% of its initial capacitance after five cutting cycles and 95.1% after 1000 mechanical bending cycles. By harnessing principles of conductive self-healing and employing eco-friendly constituents derived from bio-sourced, recycled materials, our composites represent a significant advance toward sustainable, renewable alternatives to traditional petroleum-based polymer composites. Highlights: A sustainable PU elastomer from recycled PET with 97.1% BHET yield is developed. Elastomers with T_g of −64.1°C self-heal effectively via abundant hydrogen bonds. Recycled elastomer and carbon nanofillers form conductive, durable electrodes. Supercapacitors kept 94.3% capacitance after five healing and 95.1% after 1000 bends. These polymer composites offer renewable alternatives to petroleum-based polymers.