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BACKGROUND: Our living environment is being increasingly polluted by petroleum‐based plastics and there is an increasing demand for biodegradable food packaging. In this study, the effect of various ultrahigh‐pressure (UHP) treatments (0, 200 and 400 MPa) on the microstructure and thermal, barrier and mechanical properties of poly(lactic acid) (PLA)/ZnO nanocomposite films was studied. RESULTS: The film‐forming solution was processed using UHP technology. The crystallinity, strength and stiffness of the composite film after UHP treatment increased. In addition, barrier property analysis showed that the UHP treatment significantly (P < 0.05) reduced the oxygen permeability and water vapor permeability (WVP) coefficient of the PLA/ZnO nanocomposite film. Furthermore, the WVP value of the film treated at 400 MPa (50 g kg−1 nano‐ZnO content) was the lowest and reduced by 47.3% compared with that of pure PLA film. The improvement in these properties might be due to the interaction between nano‐ZnO and PLA matrix promoted by UHP treatment. CONCLUSIONS: Therefore, the application of UHP technology on the film‐forming solution could improve the crystallinity and functional properties of the nanocomposite film, and has great potential in the production of food packaging films with ideal functions. © 2021 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Poly(lactic acid) (PLA) is the most suitable for biodegradable packaging film because of its excellent integrated property, but the poor gas barrier property is its weakness. In this study, a nanocomposite film based on PLA incorporated with 0‐, 1‐, 3‐, 5‐, 10‐, or 15‐wt% nano‐Ag was developed. Effect of multiscale structure on the barrier properties of PLA/nano‐Ag films was studied. The PLA nanocomposite film with 5‐wt% nano‐Ag had the lowest water vapor permeability (WVP) value. Oxygen transmission rate (OTR) value for PLA nanocomposites with 3‐wt% nano‐Ag was found to be the lowest among all the samples. Multiscale structure was demonstrated by the scanning electron microscopy, Fourier transform‐infrared spectroscopy, X‐ray diffraction measurement, and differential scanning calorimetry results. The crystallinity of the PLA phase increased with the content of nano‐Ag in the PLA composites. The evolution of the PLA phase crystallinity could improve the barrier properties of PLA/nano‐Ag composite films for food packaging applications. From the view of multiscale structure, it is better to achieve a balance among short‐range conformation in the amorphous region, long‐range‐ordered structure, and ordered aggregated structure to improve the barrier properties of PLA/nano‐Ag composite films. [ABSTRACT FROM AUTHOR]

The effect of biobased poly(lactic acid) (PLA)/poly(ɛ-caprolactone) (PCL) blend films with different cinnamaldehyde contents (0, 3, and 9 wt%) on the physicochemical and microbial quality of button mushrooms ( Agaricus bisporus ) stored at 4 ± 1 °C for 16 days was investigated. The low-density polyethylene (LDPE) film was used as the control. The microbial levels and physicochemical properties such as weight loss, firmness, total soluble solids, O 2 and CO 2 concentrations, microbiological quality, color, and sensory quality of mushrooms were measured. Although the highest weight loss (3.08%) was observed in the PLA/PCL/C9 treatment at the end of storage, it was still lower than 5%. Mushrooms packaged in the PLA/PCL/cinnamaldehyde blend films were significantly ( p < 0.05) firmer than those packaged in the control and PLA/PCL film. The CO 2 level inside the PLA/PCL film with cinnamaldehyde was lower than those inside the control and PLA/PCL film, but the O 2 level was similar in all packages. The PLA/PCL/C9 film was more effective in reducing microbial counts and preserving the color of mushrooms than the other three films. The overall acceptability of mushrooms packaged in the PLA/PCL/C9 film still remained good and within limit of marketability after 12 d of storage. The results suggested that the PLA/PCL/C9 film with higher water vapor permeability could be used to maintain the quality of fresh button mushroom and extend its postharvest life. [ABSTRACT FROM AUTHOR]

Antimicrobial active films based on poly(lactic acid) (PLA) were prepared with poly(e-caprolactone) (PCL) and thymol (0, 3, 6, 9, and 12 wt%) by solvent casting methods. The films were characterized by thermal, structural, mechanical, gas barrier, and antimicrobial properties. Scanning electron microscopy analysis revealed that the surface of film became rougher with certain porosity when thymol was incorporated into the PLA/PCL blends. Thymol acted as plasticizers, which reduce the intermolecular forces of polymer chains, thus improving the flexibility and extensibility of the films. The addition of PCL into the pure PLA film decreased the glass transition temperature of the films. The presence of thymol decreased the crystallinity of PLA phase, but did not affect the thermal stability of films. Water vapor barrier properties of films slightly decreased with the increase of thymol loading. The antimicrobial properties of thymol containing films showed a significant activity against Escherichia coli and Listeria monocytogenes. The results indicated the potential of PLA/PCL/thymol composites for applications in antimicrobial packaging. [ABSTRACT FROM AUTHOR]

This study aimed to reinforce the barrier performance (i.e., oxygen–gas and water–vapor permeability) of poly(lactic acid) (PLA)-based films. Acetyltributylcitrate and zinc oxide nanoparticle (nano-ZnO), serving as plasticizer and nanofiller, respectively, were blended into a PLA matrix through a solvent-volatilizing method. The structural, morphological, thermal, and mechanical performances were then studied. Scanning electron microscopic images showed a significant dispersion of nano-ZnO in PLA ternary systems with low nano-ZnO content. The interaction between PLA matrix and ZnO nanoparticles was further analyzed by Fourier-transform infrared spectroscopy. Wide-angle X-ray scattering spectroscopy demonstrated high compatibility between PLA matrix and ZnO nanoparticles. Mechanical property studies revealed good tensile strength and low flexibility. Differential scanning calorimetry curves proved that an amorphous structure mostly existed in PLA ternary systems. The improvements in barrier property and tensile strength indicated that the PLA/nano-ZnO composite films could be used for food packaging application. [ABSTRACT FROM AUTHOR]

The microstructure, thermal properties, mechanical properties and oxygen and water vapor barrier properties of a poly(lactic acid) (PLA)/nano-TiO2 composite film before and after high pressure treatment were studied. Structural analysis showed that the functional group structure of the high pressure treated composite film did not change. It was found that the high pressure treatment did not form new chemical bonds between the nanoparticles and the PLA. The micro-section of the composite film after high pressure treatment became very rough, and the structure was depressed. Through the analysis of thermal and mechanical properties, high pressure treatment can not only increase the strength and stiffness of the composite film, but also increase the crystallinity of the composite film. Through the analysis of barrier properties, it is found that the barrier properties of composite films after high pressure treatment were been improved by the applied high pressure treatment. [ABSTRACT FROM AUTHOR]