Materials Advances
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Cellulose nanofibril-based hybrid coatings with enhanced moisture barrier properties †
Cite this: Mater. Adv. , 2025, 6 , 2833
Jingxuan Zhang and Jeffrey P. Youngblood *
Cellulose nanomaterials have garnered significant attention as the next generation of environmentally friendly packaging materials because of their abundance, biodegradability, low density, superior mechanical properties, and excellent oxygen barrier characteristics. However, due to their hydrophilic nature, CNMs exhibit poor water barrier properties at high humidity conditions, which limits their potential applications. Our previous research has successfully incorporated CNF with CMC and coated the CNF/CMC coating on molded pulp trays for food packaging, but the barrier properties of CNF/CMC were weakened under high humidity conditions due to the hydrophilic nature of the coating and plasticization effect of the water molecules during the permeation process. In this study, we enhanced the water barrier properties of CNF-based coatings on molded pulp trays by chemically modifying the CNF through crosslinking with polyamide-epichlorohydrin (PAE), the incorporation of Cloisite-Na + nano-clay, and the addition of polyvinyl alcohol (PVA). This formulation further improved the water vapor transmission rate (WVTR) in both wet-cup and dry-cup conditions, showing 40.5% in wet WVTR and 89.2% in dry WVTR values compared to unmodified CNF/CMC coatings. The chemical modification also helped enhance oxygen barrier performance, in which OP decreased from 6.48 10 15 cm 3 [STP] cm cm 2 s 1 Pa 1 to 2.31 10 15 cm 3 [STP] cm cm 2 s 1 Pa 1 . A reduction in Cobb value from 137 9 gm 2 to 56.3 4.4 gm 2 was also observed. The formulated CNF-coated MP trays maintained the same #12 oil and grease resistance level as the unformulated ones. Mechanical testing proved that the formulated CNF coated tray samples showed 23.3% increase in ultimate tensile strength, 96.7% increase in strain at failure, but 37.6% decrease in Young’s modulus. These results demonstrate that our chemically modified CNF coatings offer a promising sustainable alternative to conventional synthetic packaging materials, particularly for food packaging applications requiring enhanced barrier properties at high humidity conditions.
Received 23rd December 2024, Accepted 17th March 2025
DOI: 10.1039/d4ma01276c
rsc.li/materials-advances
1. Introduction The ubiquity of plastic products in modern society has led to a global environmental crisis, as discarded plastic items and microplastics accumulate in terrestrial and aquatic ecosystems, harming wildlife through entanglement, ingestion, and the leaching of harmful chemicals. 1–3 While the convenience and low cost of plastics have made them indispensable, their durability and resistance to degradation have resulted in the widespread pollution of even remote environments. 4 As the environmental impacts of plastic pollution have become increasingly apparent, researchers have begun to explore alternative materials that might replace conventional plastics. One promising class of materials is cellulose nanomaterials (CNMs). 5
CNMs exhibit unique physical and chemical properties, including high strength, low density, and biodegradability, which makes them attractive candidates for a wide range of applications. 6–8 Unlike petroleum-based plastics, CNMs can be produced from renewable and sustainable feedstocks, offering a potential solution to the growing plastic waste problem. Among the various types of CNMs, cellulose nanofibrils (CNFs) have garnered significant attention due to their excep- tional mechanical properties and versatility. 9 CNFs are typically produced through mechanical fibrillation or chemical pre- treatments followed by mechanical processing, resulting in high-aspect-ratio nanofibers with widths ranging from 4 to 20 nm and lengths ranging from 500 to 2000 nm. 6,10 The high surface area and strong hydrogen bonding capabilities of CNFs allow for the formation of robust, interconnected networks that can impart strength and barrier properties. 11 One of the most promising attributes of CNFs for packaging applications is their excellent oxygen barrier properties. This characteristic is particularly valuable in food packaging, where maintaining low
School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA. E-mail: zhan4128@purdue.edu, jpyoungb@purdue.edu † Electronic supplementary information (ESI) available. See DOI: https://doi.org/ 10.1039/d4ma01276c
Mater. Adv. , 2025, 6 , 2833–2844 | 2833
© 2025 The Author(s). Published by the Royal Society of Chemistry
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