A Direct Synthesis Route of Thermally Expanded Graphene for Electrically Conductive PEEK Polymer Composites with Environmental Assessment Analysis

Year 2025, Volume: 12 Issue: 4, 207 - 220, 01.12.2025

Semih Doğan

https://doi.org/10.18596/jotcsa.1722180

Abstract

This study presents a rapid and chemical-free synthesis of thermally expanded graphene (TEG), which is a lightweight carbon material, via 5-minute single-step thermal exfoliation of commercially available expandable graphite. The resulting TEG exhibits ultralow density of 0.0195 g/mL and a significant volumetric expansion ratio (32-fold), indicative of a porous network structure. Structural analyses confirmed the effective removal of oxygen-containing groups (C/O ratio increased from 4.7 to 79.0), restoration of conjugated graphitic domains (I2D/IG value of 0.57), the material's thermal robustness (single major decomposition stage beginning at 595 °C), and the formation of wrinkled layers with microholes resulting from gas release. Importantly, a life cycle assessment (LCA) revealed a moderate global warming potential (0.0233 kg CO₂-eq/g), substantially lower than that of reduced graphene oxide (rGO) and carbon nanotubes (CNTs). For the first time, TEG was incorporated into polyetheretherketone (PEEK) to fabricate conductive polymer composites, achieving an electrical conductivity of 0.003381 S/cm at 10 wt.% loading. These findings highlight TEG as a sustainable and high-performance conductive filler for advanced thermoplastic applications in polymer matrices.

Keywords

Expandable graphite , volumetric expansion , polymer composite , electrical conductivity , life cycle assesment.

Thanks

I would like to extend my heartfelt thanks to Prof. Dr. Burcu Saner Okan from Sabancı University, Faculty of Engineering and Natural Sciences, and Integrated Manufacturing Technologies Research and Application Center & Composite Technologies Center of Excellence for her support in providing access to laboratory facilities. In addition, special thanks to Dr. Havva Başkan Bayrak from the same center for her valuable assistance with the Life Cycle Assessment results. For electrical conductivity measurements, I also extend my sincere thanks to Dr. Mohammad Sajad Sorayani Bafqi from Sabancı University.

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