INFLUENCE OF COAT WEIGHT AND BASESHEET PROPERTIES ON BARRIER PERFORMANCE IN PAPER AND PAPERBOARD FOR FOOD-CONTACT APPLICATIONS, TAPPICon26

This work examines how basesheet properties and topcoat coating thickness influence liquid water, moisture, and oil barrier performance in paper and paperboard constructions intended for food‑contact applications. Two experimental studies were conducted: (1) a coat‑weight study using a moderate‑barrier system on paper and board substrates, and (2) a basesheet study using a high‑barrier coating system applied to seven commercially relevant paperboard grades. Across the moderate‑barrier systems, increasing topcoat weight from 5.5 to 7.0 gsm produced minimal or inconsistent improvements in moisture or liquid water resistance, indicating that poorly optimized coating systems may not benefit from additional thickness. The high‑barrier system demonstrated that basesheet properties—including porosity, roughness, bulk, ash content, and intrinsic water absorption—can influence final barrier performance, even when coating formulation and application method are held constant. Oil resistance was generally independent of basesheet selection, moisture barrier correlated most strongly with total applied coat weight, and liquid water barrier showed partial dependence on basesheet porosity and uncoated sheet Cobb values. Results highlight that barrier performance arises from a complex interplay between coating chemistry, coat weight, application technique, and basesheet characteristics. Optimized performance therefore requires matching coating systems with compatible substrates rather than relying on increased coat weight alone.