Degree of dispersion monitoring by ultrasonic transmission technique and excitation of the transducer's harmonics

• Main Authors: Schober, G, Heidemeyer, P, Kretschmer, K, Bastian, M, Hochrein, T
• Format: Conference Proceeding
• Language: English
• Subjects: Agglomerates; Beads; Calcium carbonate; Calcium compounds; Correlation analysis; Damping; Excitation; Extinction; Glass; Harmonics; Mechanical properties; Melts; Monitoring; Particle size; Polymer melts; Polymers; Resonant frequencies; Ultrasonic transducers
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/1.4873727

The degree of dispersion of filled polymer compounds is an important quality parameter for various applications. For instance, there is an influence on the chroma in pigment colored plastics or on the mechanical properties of filled or reinforced compounds. Most of the commonly used offline methods are work-intensive and time-consuming. Moreover, they do not allow an all-over process monitoring. In contrast, the ultrasonic technique represents a suitable robust and process-capable inline method. Here, we present inline ultrasonic measurements on polymer melts with a fundamental frequency of 1 MHz during compounding. In order to extend the frequency range we additionally excite the fundamental and the odd harmonics vibrations at 3 and 5 MHz. The measurements were carried out on a compound consisting of polypropylene and calcium carbonate. For the simulation of agglomerates calcium carbonate with a larger particle size was added with various rates. The total filler content was kept constant. The frequency selective analysis shows a linear correlation between the normalized extinction and the rate of agglomerates simulated by the coarser filler. Further experiments with different types of glass beads with a well-defined particle size verify these results. A clear correlation between the normalized extinction and the glass bead size as well as a higher damping with increasing frequency corresponds to the theoretical assumption. In summary the dispersion quality can be monitored inline by the ultrasonic technique. The excitation of the ultrasonic transducer's harmonics generates more information about the material as the usage of the pure harmonic vibration.