Enhanced Electrical Properties and Impact Strength of Phenolic Formaldehyde Resin Using Silanized Graphene and Ionic Liquid

In this study, to improve the electrical properties and impact strength of phenolic formaldehyde (PF) resin, PF-based composites were prepared by mixing graphene and the ionic liquid 3-decyl-bis(1-vinyl-1H-imidazole-3-ium-bromide) (C₁₀[VImBr]₂) via hot blending and compression-curing processes. The graphene surface was modified using a silane coupling agent. The synergistic effect of graphene and C₁₀[VImBr]₂ on the electrical properties, electromagnetic shielding efficiency, thermal stability, impact strength, and morphology of PF/graphene and PF/graphene/C₁₀[VImBr]₂ composites was then investigated. It was found that the electrical conductivity of the composites significantly increased from 2.3 × 10^-10 to 4.14 × 10^-3 S/m with an increase in the graphene content from 0 to 15 wt %, increasing further to 0.145 S/m with the addition of 5 wt % C₁₀[VImBr]₂. The electromagnetic shielding efficiency of the composite increased from 4.70 to 28.64 dB with the addition of 15 wt % graphene, while the impact strength of the composites rose significantly from 0.59 to 1.13 kJ/m² with an increase in the graphene content from 0 to 15 wt %, reaching 1.53 kJ/m² with the addition of 5 wt % C₁₀[VImBr]₂. Scanning electron microscopy images of the PF/GNP/C₁₀[VImBr]₂ composites revealed a rough morphology with numerous microcracks.