The monograph is a generalization of theoretical and experimental research in the field of rheology of high molecular weight compounds and their solutions, the properties of which are considered in relation to their structure and composition. The book describes all the most important manifestations of the mechanical properties of polymers in a viscous state, which is the basis for a scientifically based calculation and selection of processing equipment in the molding of products from polymeric materials. The results of investigations of viscous properties of solutions and melts of polymers, determining their behavior in various technological processes are most detailed. The behavior of fluid polymers under conditions of single-axis stretching . is considered The monograph is intended for a wide range of readers interested in the problems of physics, mechanics and physical chemistry of polymers, as well as for engineering and technical workers engaged in the processing of plastics, forming products from rubber mixtures and obtaining fibers. The book will also be useful to students and postgraduates of higher educational institutions specializing in the relevant fields of science and technology ..