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. [ABSTRACT FROM AUTHOR]