Current progress in the production of PLA–ZnO nanocomposites: Beneficial effects of chain extender addition on key properties

ABSTRACT Poly(lactic acid) (PLA) nanocomposites characterized by multifunctional end‐use properties are of high interest as new biosourced materials for the production of smart films, fibers, and injection‐molded components. In this work, PLA–ZnO nanocomposites designed for the extrusion of films were obtained by melt‐compounding PLA with up to 5 wt % ZnO rod‐like nanoparticles, nanofiller previously surface‐treated with a specific silane (triethoxycaprylylsilane). To improve the processing and performances of nanocomposites such as their stability at high temperature, the addition of a selected chain‐extender (CE) was considered. It was revealed that the co‐addition of nanofiller (ZnO) and epoxy functional styrene‐acrylate oligomeric CE (Joncryl ® ADR 4300F) leads to a very significant enhancement of the properties (molecular, rheological, thermal, etc.) of PLA–ZnO nanocomposites. After addition of 1% CE into nanocomposites, the PLA molecular weights were found to be nearly twofold higher, while the isothermal tests (at 220 and 240°C) confirmed a significant increase in thermal stability. Because the CE plays a key role in limiting the degrading effects of ZnO, due to a gain in melt viscosity and increased molecular mass, a better ability to process nanocomposites by extrusion was found. The good nanofiller dispersion and specific end‐use characteristics owing to the presence of ZnO nanoparticles (such as UV shielding) were again confirmed on extruded films. These developments are being viewed as a promising approach that can open new perspectives in the application of PLA–ZnO nanocomposites with specific end‐use properties (UV protection, antibacterial, gas‐barrier, and self‐cleaning) at larger scale. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132 , 42480.