Ultrasonic Measurements with Rubber Compounds during Extrusion

Abstract

Abstract The dependence of the Index of Elasticity, E, the reciprocal value of sound velocity, on temperature and pressure is related to specific volume and compressibility of rubbers. The sensitivity of E towards changes of temperature and pressure was calculated, indicating a new versatile possibility for the control of rubber extruders. To confirm this, extruder experiments were carried out with an SHR compound, of which a working diagram was established showing the complete behavior of E=f(p,T). The effect of compound composition, especially of plasticizer and carbon black content, was examined. Viscosity in the extruder primarily determines changes in E. The method was shown to be applicable up to a die diameter of at least 200 mm. The method may also be applied to follow degradation of rubber compounds during mastication.