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affect the sealing strength, and therefore, a sealing process should be optimised thoroughly for each material. 4. Conclusions The present study demonstrates the performance and potential of PLAX and bioORMOCER ® multilayer coatings using pilot- and industrial-scale reverse gravure and rod coaters on two commercial base papers for food packaging applications. Both coatings exhibited strong barrier properties, significantly reducing water vapour and oxygen trans- mission rates as well as a mineral oil barrier. Sample A-POP, with its precoated base paper, generally provided barrier (WVTR of 12 g/(m 2 · day) at 23 ◦ C and 50% RH) and sealing characteristics, highlighting its suitability for applications requiring higher moisture resis- tance. The smooth surface and dense fibre structure of substrate S facilitated even coating distribution for sample S-POP, which was shown as an effective oxygen barrier performance at dry (2.3 cc/(m 2 · day · bar)) and standard conditions (3.8 cc/(m 2 · day · bar)), though further optimisation may enhance its heat sealability. A grease barrier was achieved with both samples, and the KIT value was evaluated at 12. The multilayer coating structure provided a high mineral oil barrier on both the substrates, allowing the use of recycled fibres, in- cluding minor contaminants. This study was executed utilising coating lines at a higher technical readiness level, demonstrating the potential of producing high-performance bar- rier packaging materials at a larger scale. Overall, the multilayer coatings applied on both substrates contribute to a more sustainable, functional packaging solution, offering promis- ing alternatives to conventional fossil-based barriers. These findings provide insights for future packaging development, aiming to enhance packaging integrity, prolong shelf life, and reduce the environmental impact of packaging materials. In the future, the end-of-life of the material should be investigated to confirm the biodegradability and recyclability of the multilayer structure. Additionally, testing the barrier properties at higher humidities and applying a creasing would demonstrate the performance and the convertibility of the material better. Author Contributions: Conceptualization, E.N., A.A.-H., F.S., J.A. and R.K.; methodology, E.N., A.A.-H., R.H., P.K., F.S., J.A. and R.K.; formal analysis, E.N., R.K. and J.A.; investigation, E.N., A.A.-H., R.H., P.K., F.S., J.A. and R.K.; data curation, E.N. and R.K.; writing—original draft preparation, E.N.; writing—reviewing and editing, E.N., A.A.-H., R.H., P.K., F.S., J.A. and R.K.; supervision, R.K. All authors have read and agreed to the published version of the manuscript. Funding: This study was funded by the European Union’s Horizon 2020 research and innovation programme under grant agreement N ◦ 952972. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: Data is contained within the article. Acknowledgments: We would like to thank following people who were involved in the work and gave their valuable contribution: Panu Lahtinen for microfluidisation of PLAX-dispersion, Katja Pet- tersson, Ulla Salonen and Timo Kaljunen for contribution in coating application and characterisation, Mari Leino for acquiring SEM-images, Walki Group Oy for providing the base papers and Project coordinators, and Ulla Forsström and Ilona Leppänen for reviewing the article. Conflicts of Interest: Authors Eetu Nissinen, Adina Anghelescu-Hakala, Roosa Hämäläinen, Pauliina Kivinen and Rajesh Koppolu were employed by the company VTT Technical Research Centre of Finland Ltd. Author Jani Avellan was employed by the company Walki Group Oy. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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