Abstract
At the present time there is a multitude of data indicating that when polystyrene, natural rubber, polyvinyl acetate, cellulose, starch, proteins and other high molecular weight compounds are mechanically ground up, a degradation of the polymeric chains is observed. The mechanical scission of macromolecules during grinding in a colloid or ball mill, or when they are broken down on mill rolls, proceeds most rapidly at temperatures below the range of the viscous-fluid state, since under these conditions the forces of intermolecular interaction are considerably greater than the strength of the covalent bond. However, the mechanical destruction of macromolecules is also possible through certain mechanical effects acting on solutions of polymers. Thus, for instance, the force of friction generated in the flow of a 0.05% solution of polystyrene (Mcp=6×105) in tetralin through a platinum capillary is due to the scission of macromolecules, which brings about a 30% decrease in the specific viscosity. The significant gradients in the rate and in the forces of friction and cavitation developed in polymer solution through the action of ultrasonic waves with frequencies of the order of 200–300 kilocycles/sec. are due to the mechanical scission of macromolecules of polystyrene, rubber, polyvinyl acetate, cellulose and a number of other high molecular weight compounds.