Investigation of Mechanical, Thermal and Microstructural Properties of Waste Micro-Nano Nichrome (NiCr 80/20) Powder-Reinforced Composites with Polyamide 66 (PA66) Matrix

This study investigates the mechanical, thermal, electrical, and microstructural properties of polyamide 66 (PA66) composites reinforced with waste-derived micro-nano NiCr (80/20) powders. Composites containing 2, 5, and 8 wt% NiCr were prepared using thermokinetic mixing and compression molding, followed by characterization via tensile testing, Shore D hardness, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), and thermal/electrical conductivity measurements. Results showed a progressive increase in tensile modulus, tensile strength, hardness, and thermal conductivity with increasing NiCr content, reaching maximum values at 8 wt% filler. However, elongation at break decreased, indicating reduced ductility due to restricted polymer chain mobility. DSC and FTIR analyses revealed that low NiCr loadings promoted nucleation and crystallinity, while higher contents disrupted crystalline domains. Electrical conductivity exhibited a slight upward trend, remaining sub-percolative up to 8 wt% NiCr; conductivity modulation is modest at high filler loadings. SEM-EDS confirmed uniform dispersion at low-moderate contents and agglomeration at higher levels. The use of industrial waste NiCr powder not only enhanced material performance but also contributed to sustainable materials engineering by valorizing by-products from the coatings industry. These findings suggest that NiCr/PA66 composites have potential applications in automotive, electronics, and thermal management systems requiring improved mechanical rigidity and heat dissipation.