Specific influence of polyethersulfone functionalization on the delamination toughness of modified carbon fiber reinforced polymer processed by resin transfer molding

The specific influence of polyethersulfone (PES) end-functionalization with chlorine or hydroxyl end groups at same molar mass on PES-epoxy composites based on a high-performance tetra-epoxide with di-amine hardener resin (RTM6) is investigated in terms of morphology, thermal behavior, and toughness. A model study on PES filaments embedded in epoxy precursor is first performed to compare the interdiffusion and resulting morphology upon curing. PES-OH shows a larger interdiffusion distance compared to PES-Cl in the model systems and the laminates. This effect is more pronounced at high heating rate. Cross sections and fracture surfaces of composite panels are analyzed by scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX) spectroscopy to establish the link between the microstructures and fracture mechanisms. The toughness of PES-OH-modified epoxy composites is doubled compared to unmodified reference panels, whereas the PES-Cl shows no improvement. The favorable influence of PES-OH is ascribed to enhanced miscibility, interfacial adhesion and morphology, resulting from the better affinity between hydroxyl-terminated PES and the epoxy-resin. POLYM. ENG. SCI., 59:996-1009, 2019. (c) 2019 Society of Plastics Engineers