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porosity, yet it is considered that kaolin would still negatively influence to some extent the water barrier properties. 5. Conclusions Experimental formulations filled with an increasing kaolin content were successfully obtained, applied, and tested. Due to the nature of kaolin, water barrier properties were limited, yet moisture and grease barrier properties were very good. Experimental coatings were benchmarked with commercial coatings, showing how moisture barrier was similar, whereas the grease one achieved even better results, up to double resistance. The optimal results were obtained with formulations filled with 40% by weight of kaolin. The substrate strongly affected the overall barrier performance, having a white top double-coated sub- strate showing the best results. In terms of application, however, the white top liner is of higher interest. Further studies may involve recyclability tests and the role of the final consumer, trying to understand whether such solutions truly represent viable alternatives to extrusion-coated or laminated substrates for a circular approach to paper-based packaging. Author Contributions: Conceptualization, A.M. and B.D.C.; methodology, A.M. and M.V.D.; investi- gation, A.M.; data curation, A.M.; writing—original draft preparation, A.M. and M.V.D.; writing— review and editing, A.M. and M.V.D.; visualization, A.M. and M.V.D.; supervision, M.P. and B.D.C. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: Data available on request. The data presented in this study are available on request from the corresponding author. Most data are contained within the article. Conflicts of Interest: The authors declare no conflict of interest.
AppendixA
SB-B and SA-B were FTIR analyzed. The resulting spectra are reported in Figures A1 and A2. Observing the characteristic peaks, it is easily observable how Figure A1 refers to a poly(styrene-butadiene) copolymer, whereas Figure A2 refers to a poly(styrene- acrylate) copolymer.
FigureA1. FTIR spectrum for the SB-B commercial coating.
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