Suberin-Based Aqueous Dispersions for Barrier Packaging Applications

Barrier coatings derived from synthetic polymers have been widely used as protective layers in packaging applications. In this work, water dispersions of suberin, a natural polyester of birch bark with inherent hydrophobicity properties, were revealed as a sustainable and green alternative barrier layer in fiber-based packaging. Suberin fractions were isolated from birch outer bark using a lab-scale and pilot-scale alkaline ethanol-water fractionation process, and their properties were analyzed in detail. Thermomechanical dispersing (55-75 degrees C) was then used to produce stable aqueous dispersions of suberin, which were further used in the coating of paper and paperboard substrates using a pilot-scale coating line. The impact of pH, temperature, addition level of stabilizer, and Ultra Turrax post-treatment on the dispersion stability, particle size, and rheology were assessed. Results showed that the suberin aqueous dispersion exhibited homogeneous particle size distribution in the range of 1-100 mu m, and its shear-thinning behavior benefits the pilot-scale coating process. Most importantly, the resulting suberin-coated paperboard sample showed an excellent barrier against water vapor (18 g/m(2)/day), heptane vapor (below the detection limits), grease resistance (KIT number of 12), and oil penetration (24-168 h). The results indicate that the suberin aqueous dispersion is a promising coating material for fiber-based barrier packaging applications and its barrier performance is comparable to commercial barrier dispersions.