Morphology features of biodegradable plastic–elastomer blends

Objectives. To obtain data on the compatibility of a polymer blend based on poly-3-hydroxybutyrate and butadiene-nitrile rubber for the development of a biodegradable polymer with improved mechanical properties. Methods. Film samples of biodegradable plastic–elastomer blends, using mixtures of poly-3-hydroxybutyrate and butadiene-nitrile rubber as a case study, were investigated by means of optical and scanning electron microscopy with computer-aided image analysis, differential scanning calorimetry, mathematical analysis, and Fourier transform infrared spectroscopy. Results. The mixtures studied herein were found to have a heterogeneous heterophase structure. The interaction between the carbonyl group of poly-3-hydroxybutyrate and the nitrile group of acrylonitrile block of acrylonitrile butadiene-nitrile rubber is shown due to kinetic compatibility. A change in the crystalline regions of poly-3-hydroxybutyrate when it is mixed with rubber was also noted. The results of the Gibbs energy calculation of mixing confirmed the interaction of carbonyl and nitrile groups. Microscopy results show the localization of poly-3-hydroxybutyrate particles around rubber particles. The reasons for this phenomenon are discussed here. Conclusions. Studies have shown a relationship between morphology and component content of the samples. The change in composition affects the structure and properties of the surface and volume. The formation of associates leads to the formation of an interface which attracts the second component. The Flory–Huggins theory, Avrami equations, and microscopic data established a complex interaction mechanism: convergence and formation of chemical bonds, rearrangement of crystalline regions, transition of spherulitic particles into lamellar particles, diffusion of rubber macromolecules, association of poly-3-hydroxybutyrate particles around the rubber, and completion of chemical bonds.