Comparative Analysis of Nickel‐Coated Graphite, Graphite, and Nickel in <scp>PLA</scp> / <scp>TPU</scp> Blends: Advancements in Compatibility, Conductivity, and Rheology

ABSTRACT This study presents a systematic comparison of graphite (G), nickel (Ni), and nickel‐coated graphite (NiC) as conductive fillers in polymer blends of polylactic acid (PLA) and thermoplastic polyurethane (TPU). Morphological analyses confirmed that NiC exhibited markedly better compatibility compared to G. While Ni particles appeared roughly spherical with primary sizes of 1.5–2 μm and agglomerates up to 15 μm, graphite displayed highly fragmented structures with irregular thicknesses. In contrast, NiC retained a broader particle size distribution and more intact layered morphology, indicating better structural integrity and improved interaction with the matrix. The rheological percolation threshold was determined as 14 wt% for uncoated G and 48 wt% for NiC. In the case of Ni, a clear percolation threshold could not be identified due to its distinct rheological behavior. The aspect ratio ( A f ) values calculated from the percolation threshold were 2.75 for G and 1.23 for NiC, confirming the morphological differences between the two fillers. Improved interfacial compatibility notably affected the electrical conductivity of the composites, primarily due to the conductive nature of nickel at the interface. Composites containing NiC achieved conductivity up to 10 −3 S/cm, while those with uncoated G and Ni reached 10 −6 and 10 −8 S/cm, respectively.