Viscosity and density measurement methods for polymer melts

Abstract

In this article review of density and viscosity measurement methods is presented, including ultrasonic pulse echo methods, which are capable to measure these properties of polymer melts. The methods are presented according to measurement principles, methodology, accuracy and possibility to measure density and viscosity of polymer melts on-line during extrusion process. Such measurements are very important for process automation, process monitoring and control. The ultrasonic pulse echo methods are separated from other methods, because very often they are superior to other techniques. The advantage of this technique is that at the same time sound velocity and attenuation in a plastic melt may be measured, what gives more information. For this purpose polarized shear waves as well as longitudinal, torsional and other types of waves in a wide frequency range may be employed.

Process monitoring and visualization solutions for hot-melt extrusion: a review

“…Several reviews have been published describing the general mechanisms of action of process analytical tools in pharmaceutical production processes. Readers are referred to these publications illustrating near infrared (NIR) spectroscopy, [35][36][37][38][39][40][41] Raman spectroscopy, [35,38,39,[42][43][44][45] ultraviolet/ visible (UV-VIS) spectroscopy, [35] fluorescence spectroscopy, [35] terahertz (THz) spectroscopy, [35,39,42,46,47] nuclear magnetic resonance (NMR) spectroscopy, [35] ultrasound techniques [48] and rheological techniques. [49,50] Process analytical tools for hot-melt extrusion…”

“…Monitoring of solid state and polymer-drug interactions Not possible to monitor a transparent formulation (low signal/noise ratio) [48] [ 54,60] NIR spectroscopy: transmission…”

“…In-line Monitoring of drug concentration Difficulties with collecting spectra from a non-transparent melt, [48] resulting in a high background signal [59] Post die…”

“…Monitoring of solid state and polymer-drug interactions Difficulties with collecting spectra from a non-transparent melt, [48] resulting in a high background signal [59,60] Die In-line Monitoring complex formation by an acid-base reaction - [62] Barrel segments…”

Ultrasound based monitoring of the injection moulding process - Methods, applications and limitations

“…Due to the high pressure and temperature during the injection moulding and extrusion process the development of inline monitoring systems is challenging. Nevertheless, ultrasound systems were used in polymer processing for the estimation of the polymer melt temperature [1], viscosity and density measurements [2], monitoring the melting process of polymer in an internal mixer [3] or along the screw [4] and for the detection of spots and gel particles [5]. The thermal and mechanical homogeneity of the polymer melt stored in the screw ante-chamber after the plasticizing process strongly influence the quality of the final injection molded part.…”