Torque Relaxation and Torsional Energy in Crêpe Yarn

Earlier work has shown that there is a relation between the character of the pebble in rayon crêpe and the untwisting torque exerted by the yarn when wetted. In the present paper the torsional internal energy in twisted viscose yarn is investigated in detail. The torque released when thrown and set yarn is wetted is found to be independent of the commercial variation in filament number and twist. In twisting a parallel filament yarn the resisting torque due solely to internal stresses is directly proportional to the turns twist, and the corresponding torsional internal energy increases as the square of the twist. The relaxation of torque follows a simple law, the same for both the dry and wet conditions except for the constants of the equations. The torque falls off directly as the logarithm of the time. An explanation for the formation of kinks is given.