Sustainable lignin-based coatings
Packaging plays a critical role in ensuring food safety and shelf life by protecting against e.g., moisture, gases, and light. Polyethylene (PE) is widely used in food packaging, but it is mainly produced from non-renewable resources and it is an inefficient oxygen and light barrier. In a new study, the layer-by-layer (LbL) assembly of a sustainably produced lignin-based polymer (EH) with polyethylenimine (PEI) or chitosan (CH) was used to fabricate (partially or fully) bio-based coatings with the aim of improving barrier properties of PE films. PE films were coated with a variable number of PEI/EH or CH/EH bilayers (BL) using an immersive LbL assembly method.
Improved oxygen and water vapor barrier properties
Test results showed a stepwise multilayer formation and strong interactions between the oppositely charged polymers, with PEI/EH coating having a greater amount of deposited polymer compared to CH/EH coating at the same number of BL. Overall, light barrier properties and wettability of the coated films increased with the number of deposited bilayers. Coated PE films maintained the overall thermal behaviour of PE. A number of BL of 20 was found to be the most promising based on the studied properties. Selected samples showed improved oxygen and water vapor barrier properties, with PEI/EH coating performing better than CH/EH coating.
The study has been published in Progress in Organic Coatings, Volume 182, September 2023.