Effect of a chain extender on the properties of poly(lactic acid)/zinc oxide/copper chlorophyll acid antibacterial nanocomposites

Poly(lactic acid) (PLA)/nano zinc oxide/copper chlorophyll acid (CCA) antibacterial nanocomposites with excellent mechanical properties were prepared in the presence of a chain extender named tolylene diisocyanate (TDI). The effect of the chain extender on the PLA long chain was confirmed by the increased molecular weight shown in the mass flow rate and gel permeation chromatography. Escherichia coli were adopted to examine the antibacterial ability of the blends. The effect of CCA is also discussed with regard to the enhancement of the antibacterial effect of zinc oxide (ZnO) over E. coli. Scanning electron microscopy and transmission electron microscopy were used to view the agglomeration and dispersion of ZnO in the PLA matrix. Differential scanning calorimetry and thermogravimetric analysis revealed a relatively stable thermal performance of the nanocomposites with and without TDI. A sharp increase in the mechanical properties was also observed after the addition of the chain extender under different processing conditions. Additionally, we found that the nanocomposites with the incorporation of TDI and the masterbatches in batches effectively improved the mechanical properties of PLA/ZnO/CCA without a sacrifice of the antibacterial effect. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41561.