Influence of Dispersion Medium on Interphase Network Formation and Properties of Phenolic Resin Nanocomposites

Abstract

This study investigates the influence of dispersion media (ethanol vs water) on the interphase structure and performance of phenolic resin (PF) nanocomposites reinforced with nanodiamonds (ND) and graphene oxide (GO). Although water improves initial dispersion of nanofillers through strong hydrogen bonding, residual bound water on hydrophilic surfaces of ND and GO acts as a physical barrier. The shift of the amorphous halo toward lower angles in the XRD profiles suggests an increase in interchain distance, while the decreased glass transition temperature indicates hindered initial matrix cross-linking. The resulting curing delay shifts the postcuring reaction to higher temperatures, leading to an increase in the apparent thermal stability of the water-dispersed systems. However, the less densely cross-linked network ultimately limits mechanical reinforcement at higher filler loadings. Conversely, ethanol is readily removed during curing, promoting tighter molecular packing and a denser polymer network. Consequently, ethanol-dispersed PF/ND composites exhibited the highest reinforcement, yielding a flexural modulus of 3.7 GPa and a flexural strength of ∼150 MPa at only 0.05–0.1 wt % loading. These findings demonstrate that solvent selection governs the interphase network architecture and, ultimately, the thermal and mechanical performance of nanocarbon/polymer composites.