Green plasticizers from waste cooking oil catalytically modified by g-C 3 N 4 /graphene nanocatalysts: Implications for structure and performance of PVC

Growing environmental concerns associated with phthalate plasticizers have accelerated the development of sustainable alternatives derived from renewable resources. Herein, waste cooking oil (WCO) was catalytically tailored using g-C 3 N 4 /graphene nanostructures to regulate intermolecular interactions within poly (vinyl chloride) (PVC). The influence of nanomodification on mechanical performance, thermal stability, migration resistance, and solvent durability was systematically investigated and quantitatively correlated to structure–property relationships. Among the prepared systems, the g-C 3 N 4 /graphene-modified plasticizer (P1) produced PVC films with the highest tensile strength (6.95 MPa) and Young’s modulus (890 MPa) while maintaining adequate flexibility (elongation ≈230%). Thermal analysis revealed delayed degradation with an onset temperature near 250°C, indicating restricted chain improved thermal stability. Migration measurements showed a noticeable reduction (≈3.5%), approaching the behavior of the commercial DOP reference. FTIR and SEM analyses suggest improved interfacial compatibility between PVC and the modified plasticizer, as evidenced by C = O band shifts (5–9 cm −1 ) and a more uniform, compact morphology with reduced microvoids. The improved performance is attributed to increased polarity, stronger dipole interactions, and reduced free volume arising from epoxy functionalities and nano-induced physical networking. This work provides direct experimental evidence linking nano-assisted chemical tailoring of waste-derived oils to suppression of plasticizer mobility and enhancement of thermo-mechanical stability. The proposed strategy offers a scalable pathway toward safer and more sustainable PVC materials.