Mahdollisuudet barrier-suorituskyvyn edistyneelle mittaamiselle kuitupohjaisissa pakkauksissa

The transition from fossil-based plastics to fibre-based and bio-based packaging has increased the need for accurate evaluation of barrier performance. While essential for protection against oxygen, moisture, and grease, barrier coating performance depends heavily on coating structure, substrate properties, and environmental conditions. Standardized methods like oxygen transmission rate (OTR) and water vapour transmission rate (WVTR) were designed for plastic films and present challenges when applied to porous, heterogeneous fibre-based materials. This thesis investigated barrier property measurement techniques and the influence of surface topography on results. The study combined a literature review with a laboratory case study on coated paperboard. The review analysed OTR, WVTR, liquid resistance, and surface energy - focusing on repeatability when film-based standards are applied to paperboard. The laboratory work compared a commercial aqueous dispersion coating with nanocellulose-based coatings (CNF, TEMPO-CNF, and acetylated NFC) at various coat weights. Samples were characterized using Bendtsen roughness, air permeability, and length-scale-resolved surface variation (OSD). WVTR was measured at 50% and 80% relative humidity. Results showed that coating chemistry governed topography development. The dispersion coating levelled fine surface features and achieved the lowest WVTR. Conversely, CNF coatings increased macro-roughness with higher coat builds and showed significant WVTR deterioration at elevated humidity. Improved WVTR did not always correlate with lower air permeability, indicating a decoupling be-tween common structural indicators. This research demonstrates that reliable barrier evaluation of coated paperboard requires controlled conditioning, effective sealing, and interpretation that accounts for specific surface structures and material heterogeneity.