Enhancing long-term biodegradability and UV-shielding performances of transparent polylactic acid nanocomposite films by adding cellulose nanocrystal-zinc oxide hybrids.

We investigated UV-shielding performances and biodegradation abilities under controlled hydrolytic, soil burial, and thermal conditions of transparent polylactic acids (PLA) nanocomposite films embedded with cellulose nanocrystal-zinc oxide (CNC-ZnO) hybrids. By adding high content of 15wt %CNC-ZnO hybrids into the PLA matrix, the highest UV radiation was blocked out by (85.31%) of UV-A and (95.90%) of UV-B. It is found that the weight loss of PLA nanocomposites after being hydrolytic degraded for 70 days increased from 9% for PLA to 25% with 15 wt% CNC-ZnO hybrids. Meanwhile, in soil burial test, pure PLA shows smallest degradation rate with only 8% weight loss after 110 days, while the PLA nanocomposite film with 15 wt% CNC-ZnO hybrids was degraded by about 28%. Besides, the resultant degradation byproducts from the thermally-decomposed catalysis have been identified by Fourier transform infrared spectroscopy (FT-IR). Moreover, the morphologies and appearances changes during the hydrolytic and soil degradation of PLA nanocomposite films were evaluated. This study is expected to provide meaningful insights into nanocomposite films embedded with CNC-ZnO hybrids as a result of contourable degradation and high ultraviolet protection factor value (UPF).

Green one-step synthesis of ZnO/cellulose nanocrystal hybrids with modulated morphologies and superfast absorption of cationic dyes.

Zinc oxide/cellulose nanocrystal (ZnO/CNC) hybrids with modulated morphologies were prepared by using bamboo CNC as templates via green one-step technique. The effect of pH values on the morphology, microstructure, thermal stability, antibacterial efficiency and dye absorption kinetics of hybrids were investigated. A possible mechanism for various hybrid morphologies at different pH values was provided. All the samples exhibited high antibacterial ratios of 91.4%-99.8% against both Escherichia coli and Staphylococcus aureus. ZnO/CNC8.5 gave quick removal efficiency with high dye removal ratios in methylene blue (MB, 93.55%) and malachite green (MG, 99.02%), especially >91.47% and 97.85% within 5 min. The absorption capacity could reach up to 46.77 mg/g for MB and 49.51 mg/g for MG. Besides, absorption kinetics showed that the absorption behavior followed the pseudo-second-order kinetic model (R2 > 0.99996). Such ZnO/CNC hybrids show outstanding and low-cost adsorbent for efficient absorption of cationic dyes in wastewater treatment field.