Birch-Bark Suberin-Reconstructed Polyester Film as Packaging Materials

Fossil-based polymers dominate the packaging industry thanks to their performance and low cost. However, their negative impact on the biosphere demands a paradigm shift in the industry. Nature may provide an alternative in the form of suberin. Suberin is an amorphous polyester present in plants, where it contributes to controlling the water and gas exchange with the environment. The bark is rich in suberin, and it represents a large byproduct of the forestry industry; hence, it is a potential source of renewable monomers for the synthesis of packaging materials. In this study, we demonstrated that unrefined suberin monomers, extracted from birch bark, could be exploited to synthesize a cross-linked polyester film through a standard melt polycondensation and compression molding process. The polyester film resulted in being translucent while blocking UV radiation and having an elastomer-like behavior. The average measured water vapor transmission rate of 2660 g mu m day-1 m-2 was comparable to other polyesters, such as polylactide (1500-2000 g mu m day-1 m-2) and polycaprolactone (2653 g mu m day-1 m-2) at 23 +/- 2 degrees C, with an imposed gradient of 0-50% relative humidity. Finally, the thermal gravimetric analysis showed the absence of any unreacted suberin monomers, and although specific migration tests are required, these suberin-reconstructed polyester films are potential candidates for packaging applications.