Qiao Hu, Sudre Guillaume, Lu Bo, Maazouz Abderrahim, Lamnawar Khalid
Universite Claude Bernard Lyon 1, INSA Lyon, Université Jean Monnet, CNRS UMR 5223, Ingénierie des Matériaux Polymères F, 69621 Villeurbanne Cédex, France.
Zhengzhou University, National Engineering Research Center for Advanced Polymer Processing Technology, 450002 Zhengzhou, China.
ACS Appl Mater Interfaces. 2025 Apr 2;17(13):20162-20174. doi: 10.1021/acsami.4c22868. Epub 2025 Mar 20.
In this work, a novel and pioneering route was developed for the large-scale fabrication of PLA-based multilayer films with high barrier properties by forced assembly layer multiplication coextrusion. The process involved coextruding cellulose nanocrystal (CNC)-filled polylactide (PLA) biocomposite, obtained by a liquid feeding method, with highly crystalline poly(3-hydroxybutyrate--3-hydroxyvalerate) (PHBV) into alternating multilayer structures with a number of layers up to 513. The degree of CNC dispersion in the PLA/CNC-based composite and the multilayer architecture were first evaluated by TEM observations. Subsequently, the role of PHBV layers under confinement on the crystallization behavior and gas permeability was thoroughly investigated. It was found that the obtained films basically maintained their multilayer structure and architectures, with CNC particles overall well-dispersed at a mean length of 318 nm. Nevertheless, layer instability and breakup began to occur at 129 layers due to the formation of microscale CNC aggregates. The geometric confinement effect resulted in a gradual restriction of crystallization behavior of both PLA and PHBV phases/layers as the number of layers increased. Notably, an increase in the oriented edge-on lamellar/crystal structure in the PHBV layer along the normal direction was detected. Consequently, a remarkable reduction in oxygen transmission rate (OTR) was realized when increasing the number of layers and confinement. Additionally, multimicro/nanolayers with the large number of layers exhibited higher flexibility, while maintaining a considerable tensile strength. In conclusion, this study provides the innovative and novel solution for the continuous melt-processing of biodegradable flexible films with enhanced barrier properties, making them highly suitable for food packaging applications.
