Processing and Characterization of Copper Reinforced Cyclic Olefin Copolymer Filaments for <scp>3D</scp> Printing

ABSTRACT This study presents the development and characterization of copper microparticle‐filled cyclic olefin copolymer (COC) composites as functional filaments for fused filament fabrication. Filaments containing up to 20 wt% copper were produced via melt extrusion, maintaining consistent diameter and surface quality, demonstrating excellent processability. Thermal analysis showed negligible impact of copper on COC's glass transition temperature and only a marginal change in decomposition onset (≈459°C), while remaining over 100°C higher than polylactide/copper analogues. Melt flow rate increased with copper content, enabling high‐load extrusion without plasticizers or compatibilizers. Mechanical testing showed that at 20 wt% copper, tensile strength increased by 15% and Young's modulus by 7% relative to pure COC, while elongation at break was largely preserved, achieving a rare combination of stiffness and ductility in metal‐filled thermoplastics. Scanning electron microscopy revealed uniform dispersion of spherical copper microparticles (≤ 63 μm). Despite copper's high density (8.96 g/cm 3 ) relative to COC (1.02 g/cm 3 ), the composites remain lighter than metals, offering a favorable compromise between weight and enhanced performance. The synergy between COC's thermal stability, processability, and copper's functional contribution establishes a platform for mechanically robust and thermally stable filaments suitable for electronic housings, sensor enclosures, and biomedical devices.