Ultrasonic Monitoring of Polymer Properties from the Melt to the Solid State: Influence of Chemical/Structural Details

An ultrasonic technique is described for the simultaneous measurement of specific volume, V, sound velocity, v, and attenuation, a, at frequencies between f = 0.5 and f = 15 MHz, in a wide range of temperature (- 150 to + 400°C) and pressure (up to 2 kbars). The results (V,v,a) are translated into a complex modulus, M* = M’ + iM” and analyzed in terms of the thermodynamic state of the material. Typical results for amorphous and semi-crystalline polymers are presented which show that the technique is a probe of the fundamental features of these materials (glass transition, crystallization, melting, molecular structure) which determine processability and end use properties. The method should prove of great interest for quality and process control.