METHOD FOR DETERMINATION OF HEAT RELAXATION STRESS AND SHRINKAGE FORCE IN ORIENTED POLYMERS

摘要

The invention refers to methods of physical research, which aid in the measuring of internal tension inside materials made of oriented polymers. The measurement could be carried out when polymer is heated in isothermal mode (at constant value). Or the invention could aid in the measurement of thermo-contraction powers, which could be determined after residual stress value, when material of oriented polymer is thermo-contracted and then cooled off in isothermal mode.According to the offered method, dependence of ultrasound wave speed on the temperature is measured in non-oriented and oriented polymer materials, then the derivative of the speed difference (after temperature) is calculated, which shows the thermo-relaxation tension level and thermo-contraction power value. The abovementioned values could be determined in pre-oriented and fixed samples with definite length, by measuring in the direction of orientation. The offered method decreases labor-intensiveness, time spent on measurements, simplifies the measuring process itself and provides an opportunity to perform a non-destructive inspection of wall-less profile-type polymer materials.