The effect of biodegradable coatings on the barrier properties of papers

The objective of this work was to compare barrier property of biodegradable coatings on two base papers. Two different paper grades differing in structure (Kraft liner and printing & writing papers) were used. The papers are made in Mazandaran wood and paper industry. Coating materials with 30% solid content, included clay (100 parts) and cationic starch (12 parts), and they were mixed with two binders (PLA 10 parts and PVA 10 parts) for two formulations. The immersion method in both levels 1 and 2 minutes and two coating formulations were applied on papers. Then, the treated samples were dried in standard conditions of temperature (25◦C) and 54% humidity in the room. For that purpose, air resistance or porosity, thickness, mass, and Cobb60 were determined. As expected, time of treatment, reduced porosity and increased coating weight, but in terms of barrier properties, combination containing PVA was more effective than PLA. In comparison to the control group, all the treated samples had higher air resistance and water absorption, which the increment of water absorption is due to increased capillary in texture paper. The analysis of results showed that the immersion coating factors had considerable effects on performance of air resistance improvement and coating weight of papers. Then, calculated values of the thickness and density of coating were evaluated, which confirmed the status of water absorption. The treatments greatly increased the wettability of the surface by water.