Development of polyhydroxyalkanoate/ZnO nanocomposites via miniemulsion

Abstract

Methodology Context Polyhydroxyalkanoates (PHAs) show great potential as packaging materials due to their bio-based and biodegradable nature. The copolymer poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) is very promising because of its flexibility and intermediate barrier properties. However, novel processing techniques and development of PHBHHx as active packaging material remain relatively unexplored. Adding zinc oxide (ZnO) nanoparticles (NPs) to the polymer matrix is a known approach to introduce functional properties, such as UV barrier and antimicrobial activity, but optimal dispersion of the nanoparticles remains precarious. Therefore, we aim to explore the miniemulsion and solvent evaporation to produce PHBHHx/ZnO nanocomposite films via melt-processing and ultrasonic spray coating (USSC), with applications in food packaging. PHA surfactant ZnO water chloroform ultrasonication solvent evaporation hybrid PHBHHx/ZnO particles 10 20 30 40 150 175 200 225 250 wt.% ZnO Z-average (nm) 186 198 202 224 0.15 0.14 0.16 0.20 0.0 0.1 0.2 0.3 0.4 0.5 PDI 5 6 7 8 150 175 200 225 250 wt.% PHBHHx Z-average (nm) 186 199 219 231 0.15 0.15 0.18 0.24 0.0 0.1 0.2 0.3 0.4 0.5 PDI Conclusion Outlook • Hybrid particle size is dependent on PHBHHx and ZnO concentration and good dispersion of ZnO in hybrid particles up to 40 wt.% is apparent. • Processing of particles with extrusion results in translucent films with similar thermal and mechanical properties compared to PHBHHx, retaining flexibility (1-10 wt.%) and with a concentration dependent UV barrier effect. • Hybrid particles are successfully processed onto PHBHHx surfaces with USSC using aqueous inks. Annealing at 145°C smoothens the coating. • Coatings exhibit increased UV barrier compared to blanco film. Future research will investigate the influence of ink formulation and post-processing on the morphology of the hybrid PHBHHx/ZnO coatings. In addition, the functional properties of the coatings for packaging applications (gas barrier, antibacterial and wetting properties) will be investigated. 200 300 400 500 600 700 800 0 5 10 15 20 25 Transmittance (%) Wavelength (nm) PHBHHx 1 wt.% ZnO 3 wt.% ZnO 5 wt.% ZnO 5 wt.% ZnO-ME 10 wt.% ZnO Visible range