Build Orientation Dependent Dielectric Properties of 3D Printed PUAR/CuO/Graphite Composite Discs

Abstract

Polyurethane acrylate resin discs with Copper Oxide (CuO) and Graphite fillers of different growth orientations from 0° to 90° are fabricated using Digital Light Processing (DLP) 3D printing technique to study their dielectric properties. Three different composites, Polyurethane Acrylate Resin (PUAR)/CuO (PUA-1), PUAR/CuO/ Graphite (PUA-2), and PUAR/Graphite (PUA-3), with 1 wt% total filler concentration, are prepared for the present study. X-Ray Diffraction (XRD) analysis of composites shows peaks, 2θ ~ 20.4° (PUAR), 35.4° and 38.6° (CuO), and 26.4° (graphite). Fourier Transform Infrared (FTIR) analysis reveals intensity reduction of C=O and C=C peaks, while the Raman spectrum shows a shift by 20 ± 5 cm^-1 in PUA-1, 2, and 3, confirming filler interaction with PUAR and phase modification due to polymer-filler interface. Thermo-gravimetric analysis indicates a strong interaction between the filler and the resin, especially for PUA-3, with degradation in two stages at 320 °C and 430 °C due to hard-and soft segment decomposition. Capacitance measurements at 100 kHz and 1 MHz indicate a higher dielectric constant for PUA-3 than for PUA-0, which decreases with increasing build orientation and reaches a minimum at 45°. Anisotropy due to the build and filler orientation is studied using space-charge polarization. The equivalent circuit for dependence on build orientation is understood in terms of capacitances due to fillers, represented by a Constant Phase Element (CPE), with both perpendicular and parallel components contributing to the composite disc's capacitance. With an increase in build orientation angle, the interfacial polarization decreases and so capacitance, CPE₀ >> CPE_x > CPE₉₀. Finite Element Analysis (FEA) further examines build orientation-dependent filler-resin interaction, and dielectric properties show dependence on both filler morphology and build angle. FEA highlights the role of orientation-dependent space charge distribution and Maxwell-Wagner-Sillars interfacial polarization, driven by filler morphology and alignment, in governing dielectric anisotropy. FEA corroborates the experimental observations, showing that space-charge accumulation at filler-matrix interfaces is maximal for 0° build orientation, where graphite flakes are perpendicular to the electric field, and minimal for 45°-90°.