Sonochemical Synthesis of Poly(lactic acid) Nanocomposites with ZnO Nanoflowers: Effect of Nanofiller Morphology on Physical Properties

Abstract

This study reports the ultrasound-assisted synthesis of PLA/ZnO nanocomposites with the special feature of a flower-like morphology of ZnO. The ZnO nanoflowers were synthesized via a facile sonochemical method with Zn(NO3)2·6H2O as precursor in different concentrations of 0.025, 0.05, 0.075, and 0.1 M. The as-synthesized ZnO had a flower-like morphology with petals of thickness ≈ 21 nm, width in the range of 200–800 nm, and total BET surface area of 19.87 m2 g–1. Films of PLA/ZnO nanocomposites were synthesized with an ultrasound-assisted solution casting method. Characterization of the nanocomposites revealed excellent thermal, optical, and mechanical properties at a very low loading of ZnO (0.5 wt %): tensile strength = 26–32 MPa, % elongation = 2.9 to 4.7%, highest degradation temperature = 298 °C, glass transition temperature = 52 °C, reduction in UV transmittance (absorption edge 368 nm) = 95%. In addition, PLA/ZnO nanocomposite films possessed efficient antimicrobial properties with >99% reduction of both Gram-negative and Gram-positive bacteria (Escherichia coli and Listeria. monocytogenes) in just 12 to 18 h. These properties are attributed to high interfacial interactions between nanofiller and the PLA matrix resulting from special morphological features of ZnO nanoflowers, and also uniform dispersion of ZnO nanoflowers in the PLA matrix under the influence of sonication.