Development and characterization of novel poly(ether ether ketone)/ZnO bionanocomposites

Novel poly(ether ether ketone) (PEEK) based nanocomposites with different contents of ZnO nanoparticles were prepared via cryogenic ball-milling followed by compression moulding. The nanoparticles were treated with a silane coupling agent to improve their dispersion and interfacial adhesion with the matrix. The morphology, thermal, mechanical, tribological and antibacterial properties of nanocomposites with raw and modified ZnO were comparatively investigated. A progressive rise in the thermal stability and flame retardant ability was found with increasing ZnO loading, the improvements being more pronounced for composites incorporating the coupling agent. The addition of small ZnO contents raised the crystallization temperature and the degree of crystallinity of PEEK, while at higher concentrations the nanoparticles confined the mobility of the polymer chains, hindering the crystal growth. Composites with silane-treated ZnO displayed superior stiffness, strength, ductility, toughness and glass transition temperature with reduced coefficient of friction and wear rate compared to the neat polymer and samples with bare nanoparticles. At a critical concentration of 5.0 wt% of functionalized ZnO, the tensile strength, Young's and storage moduli showed a maximum that coincided with the highest crystallinity and the minimum in the tribological properties. The antibacterial activity against Escherichia coli and Staphylococcus aureus was enhanced with increasing ZnO content, and the best antibacterial property was obtained with 7.5 wt% of modified nanoparticles.