Waterborne rod-coated PVA/starch thin films with zeolite microfillers: processing and structure–property relationships

Polyvinyl alcohol (PVA) is a promising matrix for water-based functional films and coatings, mainly in sustainable packaging, yet its potential applications are generally limited by its properties that are further highly sensitive to hydrophilic additives and inorganic fillers. Here, ∼20 μm PVA-based films were produced by rod coating from aqueous formulations containing glycerol as plasticizer and either starch (10 wt% of total polymer) and/or synthetic zeolite microfillers (4A or 13X, 2–4 wt% on polymer basis). An ATR–FTIR “up–down” approach identified formulation windows that ensured homogeneous zeolite distribution through the film thickness. All formulations yielded transparent, continuous thin films; microscopy revealed additive-induced microdefects and filler domains without loss of integrity. Thermogravimetric analysis in N2 showed increased main degradation temperatures in the case of starch and zeolite addition (up to ∼ + 60 °C), while XRD indicated low crystallinity (∼10%) with limited composition effects. Moisture-related properties remained dominated by the hydrophilic matrix (water uptake >130% after 1 h; WVTR ∼1000 g m−2 d−1). These results can provide structure–property guidance for designing waterborne PVA-based coating layers for several applications, including packaging.