Zeolite 4A/13X microfillers in waterborne PVA/starch thin films: processing, properties and soil burial degradation

Glycerol-plasticized PVA-based thin films were produced by rod-coating waterborne formulations containing 0–10 wt% starch bio-additive and/or 0–2–4 wt% zeolite 4A or 13X. An ATR‑FTIR protocol identified a processing window enabling homogeneous zeolite distribution through film thickness. Zeolites increased thermal stability (DTG Tmax shifts up to +60 °C), with a clear synergy for starch+13X (Tmax ≈ 360 °C). In wet soil burial (30 °C, 16 weeks), zeolites were microbiologically benign and did not suppress degradation; at 4 wt%, they raised overall mass loss by possibly retaining water and promoting micro‑erosion at filler–matrix interfaces. Overall, zeolite 13X resulted to be a better additive than 4A in PVA-based films; cation exchange with antimicrobial ions could be explored as well.