Structure–property correlation of TiO2/CNT–PVA hybrid nanocomposites

Abstract

This work investigates the structural, thermal, and mechanical behavior of PVA–based hybrid nanocomposites reinforced with a dual-filler system comprising 0.4 wt.% carbon nanotubes (CNTs) and varying concentrations of TiO₂ nanoparticles (NPs) (1, 3, and 5 wt.%). The nanocomposites are fabricated using a room-temperature solution casting method designed to promote uniform particle dispersion and strong interfacial interactions. XRD analysis confirmed the integration of CNT and anatase TiO₂ phases within the polymer matrix, while FTIR spectroscopy revealed characteristic shifts in O–H and C=O stretching bands, indicating hydrogen bonding and the formation of Ti–O–C linkages. TEM micrographs demonstrated morphology-dependent dispersion behavior, with well-dispersed grains at lower TiO₂ loadings and visible agglomeration at higher concentrations. Thermal analysis showed that incorporating TiO₂ enhances the stability of the composites, with the 3 wt.% TiO₂ formulation exhibiting the most pronounced improvement in thermal conductivity (0.72 W m⁻¹ K⁻¹) and diffusivity (4.1 × 10⁻⁷ m² s⁻¹). Density measurements revealed progressive densification with increasing TiO₂ content, peaking at 1.34 g cm⁻³ for the 3 wt.% composite, accompanied by a reduction in porosity to 14.2%. Mechanical characterization further demonstrated significant reinforcement, with hardness rising from 46 Shore D for pure PVA to 62 Shore D at 3 wt.% TiO₂, and compressive strength increasing from 18.2 MPa to 29.8 MPa across the same compositions. The combined effects of CNTs and TiO₂ produce synergistic enhancements, with the 3 wt.% TiO₂ hybrid nanocomposite exhibiting the most balanced and superior thermo-mechanical performance. These findings highlight the potential of dual-nanofiller PVA systems for advanced coating, packaging, and structural applications.