Photo- and Water-Degradation Phenomena of ZnO Bio-Blend Based on Poly(lactic acid) and Polyamide 11

Abstract

The goal of this work was to investigate the morphological and chemical–physical changes induced by adding ZnO nanoparticles to bio-based polymeric materials based on polylactic acid (PLA) and polyamide 11 (PA11). Precisely, the photo- and water-degradation phenomena of nanocomposite materials were monitored. For this purpose, the formulation and characterization of novel bio-nanocomposite blends based on PLA and PA11 at a ratio of 70/30 wt.% filled with zinc oxide (ZnO) nanostructures at different percentages were performed. The effect of ZnO nanoparticles (≤2 wt.%) within the blends was thoroughly explored by employing thermogravimetry (TGA), size exclusion chromatography (SEC), matrix-assisted laser desorption ionization–time-of-flight mass spectrometry (MALDI-TOF MS) and scanning and transmission electron microscopy (SEM and TEM). Adding up to 1% wt. of ZnO resulted in a higher thermal stability of the PA11/PLA blends, with a decrement lower than 8% in terms of molar masses (MMs) values being obtained during blend processing at 200 °C. ZnO promoted trans-ester-amide reactions between the two polymers, leading to the formation of PLA/PA11 copolymers. These species could work as compatibilisers at the polymer interface, improving thermal and mechanical properties. However, the addition of higher quantities of ZnO affected such properties, influencing the photo-oxidative behaviour and thus thwarting the material’s application for packaging use. The PLA and blend formulations were subjected to natural aging in seawater for two weeks under natural light exposure. The 0.5% wt. ZnO sample induced polymer degradation with a decrease of 34% in the MMs compared to the neat samples.

Preparation of Poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide)/Zinc Oxide Nanocomposite Bioplastics for Potential Use as Flexible and Antibacterial Food Packaging

“…The resulting PLLA-T d,max and PEG-T d,max values are also summarized in Table 3 , which shows that the PLLA-T d,max peaks were significantly shifted to lower temperatures as the nano-ZnO content increased. It may be hypothesized that the ZnO nanoparticles activated depolymerization of PLLA end-blocks [ 27 , 42 , 43 ], whereas the PEG-T d,max peaks slightly shifted to lower temperatures as the nano-ZnO content increased. The TGA results support the conclusion that the addition of nano-ZnOs reduced the thermal stability of the PLLA-PEG-PLLA.…”

Understanding the Effects of Adding Metal Oxides to Polylactic Acid and Polylactic Acid Blends on Mechanical and Rheological Behaviour, Wettability, and Photo-Oxidation Resistance

“…Zinc oxide (ZnO) nanopowder (<100 nm particle size) was purchased from Sigma-Aldrich and used with further purification. According to our previous investigations, ZnO nanoparticle size spanned a 100-200 nm range, with a mix of tubular and round-shaped forms [35].…”

“…Therefore, there could be a potential negative effect on landfill disposal at the end-of-life of the micro-/nano-composites, and this highlights the need for accurate separation and management of these materials. The micro-/nano-composite materials cannot be mixed with poor polymer or biopolymer waste and must be separated for efficient and safe recycling [35].…”

Crystallization and Performance of Polyamide Blends Comprising Polyamide 4, Polyamide 6, and Their Copolymers

“…Blending is a convenient, effective, and low-cost method for improving the processability of polymeric materials and enhancing their properties [ 7 ]. Several PA blends have been reported, such as those with polypropylene [ 8 ], polyethylene [ 9 ], polyethylene terephthalate [ 10 ], polylactic acid [ 11 ], acrylonitrile butadiene styrene [ 12 ], and two types of PA [ 13 , 14 , 15 ]. Although most of these blends are immiscible, PA/PA blends are miscible.…”