Wet chemical synthesis of ZnO particles and incorporation into PHBV matrix

Biopolymers do not depend on petroleum sources and they are produced by eco-friendly routes. Therefore, they are important alternatives for conventional plastics. Polyhydroxyalkanoates (PHA) are naturally synthesized by many types of bacteria and are biodegradable and biocompatible thermoplastic polymers. One commonly studied type of PHA is polyhydroxybutyrate-co-valerate (PHBV). Despite its advantages of being completely bio-based and biodegradable, it exhibits high crystallinity, narrow processing window, and brittleness. Poor thermal and mechanical properties of PHBV are a disadvantage in packaging applications. Fabrication of polymer nanocomposites by addition of various nanoparticles into polymers are a common and promising method for improvement of polymer properties. ZnO particles are commonly studied for fabrication of polymer nanocomposites due to their high volume to area ratio, highly crystalline structure, good mechanical properties, low thermal expansion coefficient, high thermal conductivity, and antimicrobial activity. In this study, various morphologies of ZnO particles were synthesized by wet chemical synthesis method. Reaction parameters such as precursors concentration, reaction temperature, and reactor volume were studied. Effects of carboxymethyl inulin on the morphological properties of ZnO particles were investigated. Sonochemical synthesis combined with wet chemical synthesis was also studied and the effects on particle dispersion were investigated. In order to achieve uniform particle dispersion, surface modification was applied to ZnO particles and untreated and surface-treated particles were compared. Effects of ultrasonic dispersion were also analyzed in terms of particle dispersion. Synthesized ZnO particles with varying conditions were characterized by measurement of surface area, X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). ZnO particles synthesized by varying conditions were incorporated into PHBV matrix by the melt-extrusion method using a twin-screw extruder. Fabricated PHBV/ZnO nanocomposites were characterized for their structural, thermal, and mechanical properties. SEM, XRD, and FTIR analyses were utilized for structural characterization of the nanocomposites. Thermal properties of the nanocomposites were characterized by thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC). Mechanical properties were studied by tensile testing. Effects of different ZnO particles on the properties of PHBV were studied.