The book will help to get acquainted with the basic ideas about the structure and properties of polymer mixtures . Presented ideas about the thermodynamics of mixtures and the reasons for the low mutual solubility of polymers. The association of macromolecules and its influence on the properties of polymer mixture solutions. The regularities of formation of interphase layer and increase in bond strength of heterogeneous polymers by introduction of compatibilizers. The regularities of phase structure formation during mixing are considered, as well as the theory of laminar mixing, including the theory of the decomposition of a liquid cylinder in a polymer matrix. Separate chapters are devoted to the mechanical and rheological properties of mixtures, in particular the properties of impact-resistant polymers. Patterns of structure formation and properties in three-component polymer-polymer-polymer mixtures . The final chapter contains extensive information on mixtures involving biodestructible polymers. Recommended by the Educational and Methodological Association of Chemical-Technological Universities as a teaching aid in the preparation of chemists for polymer processing.