Figure 7.

Permeability of water vapor coefficients of a film based on PCL with the addition of birch tar. In the case of PCL, the reduction in the water vapor transmission coefficient, and consequently the enhancement of barrier properties, is attributed to the hydrophobic nature of birch tar. Variations in the impact of birch tar on the properties of the tested materials may stem from differences in the degree of crystallinity among the polymers used. In summary, birch tar, owing to its hydrophobic properties, can serve as an additive to polymers to reduce their water vapor transmission coefficient and, consequently, enhance the packaging’s barrier properties.