Effect of Nanocellulose Reinforcement on The Structural,Dielectric, and Electrical Breakdown of Epoxy Nanocomposites

This study investigates the influence of nanocellulose (NC) on the dielectric and ‎electric field properties of epoxy-based nanocomposites for high-voltage insulation ‎applications. Two types of NC, cellulose nanocrystals (CNC) and cellulose ‎nanofibers (CNF), were incorporated into an epoxy matrix at loadings of 0.5–5.0 ‎wt.%. Morphological analysis by scanning electron microscopy revealed uniform ‎dispersion at low concentrations and increasing agglomeration at higher loadings, ‎particularly in CNF due to its fibrous structure. Electrochemical impedance ‎spectroscopy showed that composites containing 1.0 wt.% CNC and 0.5 wt.% CNF ‎achieved optimal dielectric performance, with reduced relative permittivity (εᵣ ≈ 5.07 ‎for CNC and 5.57 for CNF), suppressed conductivity, and stable capacitive ‎behaviour. COMSOL simulations supported these findings, demonstrating reduced ‎peak electric field intensity (25.8 MV/m) at optimal loadings, indicating improved ‎field uniformity. Breakdown strength tests further confirmed the trend, with CNC ‎at 1.0 wt.% exhibiting 57.9 kV/mm (39% higher than neat epoxy) and CNF at 0.5 ‎wt.% showing 46.7 kV/mm (12% higher than neat epoxy). At higher loadings, ‎aggregation increased permittivity, field crowding, and dielectric loss, leading to ‎reduced insulation performance. Overall, CNC provided broader reinforcement ‎potential than CNF, highlighting nanocellulose as a promising sustainable filler for ‎high-performance epoxy insulation‎.