PES-grafted graphene core-shell filler for epoxy composites: Significant improvements of thermal and mechanical properties at ultra-low loadings

This study presents the synthesis of polyether sulfone (PES)-grafted graphene nanoplatelets (GNP) (CGP) and their application in epoxy composites. CGP was synthesized through a multi-step process involving the oxidation of GNPs and the chemical modification of PES, followed by covalent grafting. The successful grafting of PES onto GNP was confirmed through Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) analyses, and transmission electron microscopy (TEM) analyses. The thermal and thermomechanical properties of CGP/epoxy composites were investigated, showing a significant increase in glass transition temperature ( T g ) and storage modulus with the addition of CGP. At 0.1 phr CGP content, the T g increased by 13 °C, and the storage modulus reached its maximum at 2049.2 MPa. The flexural strength of the composites also peaked at 0.1 phr, showing a 50 % improvement over pristine epoxy. SEM analysis revealed increased surface roughness in CGP/epoxy composites, contributing to enhanced fracture toughness. Additionally, the thermal stability of the composites improved, with a 19 °C increase in maximum decomposition temperature ( T max ) at 0.1 phr. The thermal expansion coefficient (CTE) was reduced by 64 % compared to pristine epoxy, indicating strong interfacial interactions between CGP and the epoxy matrix. These results suggest that CGP can effectively improve both thermal and mechanical properties of epoxy composites, making them a promising candidate for advanced material applications. • PES was grafted onto GNP via GNP oxidation and PES amination, forming an amide linkage. • CGP formed an IPN network between PES and epoxy, improving dispersion and glass transition. • CGP increased mechanical strength, modulus, and thermal stability of the epoxy.