Fabrication and characterization approach to enhance the mechanical performance of zirconia‐coated <scp>Multi‐walled carbon nanotubes</scp> reinforced <scp>High density polyethylene</scp> composites

Abstract This study presents a comprehensive investigation into the fabrication and characterization of high‐density polyethylene (HDPE) composites reinforced with zirconia (ZrO 2 )‐coated multi‐walled carbon nanotubes (MWCNTs). HDPE, a widely used polymer for pressure pipe applications, was selected for its superior mechanical properties, while ZrO 2 ‐coated MWCNTs were employed as nanofillers to enhance these properties further. The acid functionalization of MWCNTs, followed by the application of a ZrO 2 coating, was executed to ensure optimal dispersion and interfacial bonding within the HDPE matrix. The functionalized MWCNTs (f‐MWCNTs) were synthesized via an acid treatment process using 8 M HNO 3 , which significantly eased agglomeration and facilitated a stable ZrO 2 coating. Subsequent hydrothermal processing at 200°C for 18 h yielded uniformly coated MWCNTs. These nanofillers were then melt‐blended with HDPE, followed by injection molding. Mechanical testing revealed substantial enhancements in the tensile, flexural, and hardness properties of the composites. The tensile strength exhibited a marked increase, peaking at a 3 wt.% ZrO 2 ‐coated MWCNT concentration, with a 50% improvement over pristine HDPE. Flexural modulus and hardness values also saw significant increments, with the highest enhancements recorded at 4 wt.% filler content. Impact testing showed improved toughness, although excessive filler loading led to diminished returns due to nanoparticle aggregation. FTIR and XRD analyses supported the successful integration of ZrO 2 ‐coated MWCNTs within the HDPE matrix, highlighting the presence of characteristic peaks associated with both MWCNTs and HDPE. These findings provide the potential of ZrO 2 ‐coated MWCNTs as effective nanofillers in enhancing the mechanical performance of HDPE composites, making suitable for advanced engineering applications. Highlights Coating of ZrO 2 on MWCNTs using Hydrothermal method. Melt blending of ZrO 2 coated MWCNT with HDPE using twin‐screw extruder. Preparation of samples through injection molding as per ASTM standard. Mechanical properties and characterization analysis of the composite.