Processing and Characterization of Copper Reinforced Cyclic Olefin Copolymer Filaments for 3D 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.