The present paper focuses on the study of novel blends based on poly(3-hydroxybutyrate) (PHB) and polymers with different hydrophilicity (LDPE and PA). Polymer blends were produced from five ratios of PHB/LDPE in order to regulate the resistance to hydrolysis or (bio)degradation through the control of water permeability. The relation between the water transport and morphology (TEM data) shows the impact of polymer component ratio on the regulating water flux in a hydrophobic matrix. To elucidate the role of hydrophilicity of the second component presented in the PHB blends, we studied the PHB/PA blends where PA is the polyamide resin composed of statistical copolymer of hexamethyleneadipinate and ε-caprolactam in the ratio of 1:1. The complex of techniques including DCS and FTIRimaging (for T-scale) demonstrates the interaction between PHB and PA in the temperature ranges of crystallization and melting. The general approach based on Flory-Huggins equation is presented as the way for choosing the pairs of compatible or partly compatible polymers.