Abstract The mechanical grinding, milling, mixing, homogenization, freezing and other processes of the physico-mechanical processing of high polymers are widely used in the industries of plastics, rubbers, synthetic fibers, food products, silicates and many other branches of technology. Some of these processes have a great significance in biochemistry, medicine and biology. An analysis of the available experimental data permits one to reach the conclusion that in the intensive grinding of natural polymers (cellulose, starch, proteins or synthetics (polystyrene, rubber, polyisobutylene, etc.) a mechanical scission (cracking) of the macromolecules is observed. The possibility of macromoleeular scission under the grinding of high molecular weight substances is due to the high probability of a localization of mechanical energy at different sections of the polymer chain, which under certain conditions causes internal stresses exceeding the strength of covalent or ionic bonds. Mechanical breakdown of macromolecules is possible not only with dry or wet grinding, but also by mechanical action on polymer solutions. Thus, for instance, Staudinger has shown that the high speeds and forces of friction developed in forcing a 0.005 molar tetralin solution of polystyrene, average molecular weight = Mave=6⋅106, through a platinum capillary bring about a scission of the macromolecules which is revealed in a decrease of about 30% in the specific viscosity of the solution. Forcing a solution of polyisobutylene (Mave=3.9×104–23×104) in dichlorobenzene through a capillary with a diameter of 0.2 mm causes a decrease in the intrinsic viscosity and an increase in the constant of the Huggins equation. An increase in the Mave of the polymer structure formation (cross-linking) and a repeated forcing through is conducive to the mechanical breakdown of the macromolecules. It has been established that in mixing together solutions of polymeric substances (starch, gelatine, polyvinyl alcohol, etc.) with high-speed mixers having a rotation speed of over 4000 rpm, a sharp decrease in the intrinsic viscosity [ν] is observed, while the degree of scission increases, with an increase in the rotation speed of the mixer, and also with a decrease in the concentration of the solution.