Fabrication and characterization approach to enhance the mechanical performance of zirconia-coated Multi-walled carbon nanotubes reinforced High density polyethylene composites

This study presents a comprehensive investigation into the fabrication and characterization of high-density polyethylene (HDPE) composites reinforced with zirconia (ZrO₂)-coated multi-walled carbon nanotubes (MWCNTs). HDPE, a widely used polymer for pressure pipe applications, was selected for its superior mechanical properties, while ZrO₂-coated MWCNTs were employed as nanofillers to enhance these properties further. The acid functionalization of MWCNTs, followed by the application of a ZrO₂ 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 HNO₃, which significantly eased agglomeration and facilitated a stable ZrO₂ 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.% ZrO₂-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 ZrO₂-coated MWCNTs within the HDPE matrix, highlighting the presence of characteristic peaks associated with both MWCNTs and HDPE. These findings provide the potential of ZrO₂-coated MWCNTs as effective nanofillers in enhancing the mechanical performance of HDPE composites, making suitable for advanced engineering applications. Highlights: Coating of ZrO₂ on MWCNTs using Hydrothermal method. Melt blending of ZrO₂ 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.