Investigating the Effects of Iron Oxide Nano Fillers on the Structural, Viscoelastic, and Mechanical Behavior of Additively Manufactured PDMS-Fe2O3 Composites

Abstract

Magnetoactive polymer composites have gained significant scientific attention due to their rapid and reversible reaction to external magnetic fields. This study aims to investigate the feasibility of developing Iron oxide (${Fe}_2{O}_3$) embedded Polydimethylsiloxane (PDMS) composites with direct ink writing (DIW) based 3D printing technique. PDMS-Fe₂O₃ composites with three different weight ratios of Iron oxide powder (i.e., 1%, 5%, and 10%) were formulated for 3D printing using DIW technique. The effects of varied concentrations of Iron oxide particles on the structural, mechanical, and rheological properties have been investigated. The printing parameters were kept constant with only varying printing pressure for uninterrupted printing of samples. The printing was done with a narrow-gauge needle of nozzle diameter 410 μm. The average particle size of Iron oxide was 30 nm in size, which was chosen to maintain the viscosity of the printing material low enough to avoid clogging at the nozzle. The samples structures were characterized by X-ray diffraction (XRD) analysis, rheological analysis, and tensile testing. The XRD patterns verified that ${Fe}_2{O}_3$ did not form a new crystalline phase and that the PDMS stayed amorphous. Without changing the PDMS structure, the filler remained distributed within the PDMS-Fe₂O₃ composites. Tensile data showed that higher stress values (2.8–3.04 MPa) were observed in the 1 wt% and 5 wt% Fe₂O₃–PDMS composites at the same strain as pure PDMS, suggesting enhanced strength and stiffness of printed Fe₂O₃–PDMS composites with good flexibility. The 10% Fe₂O₃-PDMS composite, on the other hand, exhibited brittle and less elastic behavior and fractured quicker at lower stresses (1–2 MPa). Although pure PDMS is the most elastic among all the samples, it exhibited somewhat reduced stress range compared to 1 wt% and 5 wt% Fe₂O₃–PDMS composites. To ensure smooth extrusion and good shape retention during 3D printing, this study also performed rheological tests to assess the viscoelastic behavior and flowability of PDMS with Fe₂O₃ inks. The stiffness and energy dissipation of PDMS were increased due to increase in both storage and loss moduli with Fe₂O₃ nanofillers.