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.

ZnO nanoparticles as chain elasticity reducer and structural elasticity enhancer: Correlating the degradating role and localization of ZnO with the morphological and mechanical properties of PLA/PP/ZnO nanocomposite

“…On the other side, recent studies reveal that ZnO‐NPs and Zn compounds can degradate a series of polyesters and, specifically, PLA during melt compounding by various mechanisms. The proposed mechanism by Murariu et al is shown in Figure . In view of that, by adding the ZnO‐NPs to the PLA blend, the matrix‐located nanoparticles can cause the PLA to undergo a degradation, leading to the decrease of molecular weight and, consequently, viscosity reduction .…”

Mechanical recycling simulation of polylactide using a chain extender

“…[12][13][14] This chain extender is a multifunctional epoxy compound that can react with nucleophilic end groups -OH and -COOH of PLA, producing a polymer with high molecular weight. [16][17][18] The use of Joncryl in PLA was also reported for clay dispersion improvement in nanocomposites, [19] for blend compatibilization, [20] for an enhancement of PLA-ZnO nanocomposites properties, [21] and in polymerization of LA using a chain extender. [16][17][18] The use of Joncryl in PLA was also reported for clay dispersion improvement in nanocomposites, [19] for blend compatibilization, [20] for an enhancement of PLA-ZnO nanocomposites properties, [21] and in polymerization of LA using a chain extender.…”

Development of Antibacterial Composite Films Based on Isotactic Polypropylene and Coated ZnO Particles for Active Food Packaging

“…Due also to low cost, ZnO particles (with sub-micro and nano-dimensions) are therefore ideal fillers for polymers to be applied in the field of active food packaging. Thus, ZnO particles have been incorporated into a number of different polymers used in food packaging [15,16], such as low-density polyethylene (LDPE) [17,18], isotactic polypropylene (iPP) [19][20][21][22][23][24], polyamide (PA) [18,25], and polylactic acid (PLA) [26].…”