Enabling the recycling of polycarbonate through reinforcement with graphene nanoplatelets

The rapid embrittlement of polycarbonate (PC) during mechanical recycling, caused by chain scission and the resulting molecular weight loss, severely limits its potential for circular use. Here, we demonstrate that the addition of graphene nanoplatelets (GNPs) enables improved recycability by simultaneously stabilizing the polymer’s molecular weight and preserving mechanical integrity. PC/GNP nanocomposites were evaluated in the as-manufactured state (R0) and after three consecutive recycling cycles (R1–R3) in terms of molecular, thermal, mechanical, and electrical properties. While neat PC exhibited catastrophic embrittlement and became too brittle for tensile testing by R3, falling apart after moulding, intermediate GNP loadings (3–5 wt. %) proved optimal. This coincides with the electrical percolation threshold (∼4.8 wt. %) and enables efficient stress transfer and crack suppression, yielding tensile strengths of ∼40–50 MPa and sustaining appreciable failure strain despite some chain scission. At higher loadings (≥7 wt. %), the Young’s modulus increased monotonically, but platelet agglomeration reduced ductility. Gel permeation chromatography (GPC) confirmed that GNPs mitigate molecular weight reduction and distribution broadening across cycles, consistent with improved macroscopic stability. Collectively, these findings establish that reinforcing amorphous polymers with percolating carbon nanofiller networks offers a viable strategy for closed-loop recycling and opens pathways toward the sustainable, high-value reuse of engineering plastics.