Balancing Processability and functional Performance of Ethylene-Modified PVOH Coatings on Kraft paper

The application of biodegradable polymeric coatings is an effective strategy to enhance the functional performance of paper-based materials while preserving their recyclability.This study investigates the relationship between polymer concentration, processability and performance of an ethylene-modified poly(vinyl alcohol) (m-PVOH) coating applied to a Kraft paper (KP) substrate.The rheology of aqueous m-PVOH solutions (5–30 wt%) were measured to assess their suitability for high-speed coating processes such as gravure and flexography, and the effect of ageing on their stability. Viscosity increased with polymer concentration, with a critical transition between 20 and 30 wt% where polymer–polymer interactions and irreversible structural rearrangements became dominant.Formulations containing 10–20 wt% m-PVOH were selected for paper coating based on the rheology and processability criteria. Higher polymer concentrations reduced impregnation into the paper matrix, leading to the formation of compact and continuous coating layers. The coated papers exhibited significantly enhanced air and water resistance, while maintaining stable oxygen and water vapour barrier properties (OTR ≈ 580 cm³/(m²·day·bar), WVTR ≈ 4 g/(m²·day)). The coatings also increased surface polarity and preserved the mechanical integrity of the substrate. m-PVOH formulations can enable scalable, recyclable, and environmentally friendly paper-based packaging solutions.