The use of a coupled rheometer and Raman spectrometer for obtaining comprehensive insight into a materials behavior is presented. Rheology is the analytical method of choice to correlate the absolute flow and deformation characteristics of a given product with its behavior towards a certain processing or application step. However, Rheology as an integral method only yields answers on the bulk of the investigated sample. It does not give any insights into what is actually happening on the molecular level during a certain processing step. Raman spectroscopy has shown its ability as a powerful, effective and non-invasive method for chemical analysis. Coupling a rheometer with a Raman spectrometer provides direct information about the molecular structure and the mechanical properties. This is extremely useful for studying the crystallization behavior of polymer melts during processing. It can also provide insight for in-situ characterization and monitoring which can be challenging when working with on-line techniques as only relative flow fields are characterized. In this contribution we present results on the melting and crystallization behavior, two common phase transitions that are critical to the flow properties of various complex fluids. These temperature-sensitive transitions are often indicated via changes in molecular conformation, while optical

measurements provide direct observation of structural characteristics. However, measurements performed on separate instruments are often challenging to correlate due to variations between samples, processing history, and temperature control. To demonstrate the capabilities of the rheo-Raman microscope we provide simultaneous Raman, rheological, and optical measurements on high density polyethylenes during crystallization as well as on a commercial cosmetic emulsion during melting and phase separation. The experimental setup represents a novel integration of commercial instrumentation: a Raman microscope (Thermo Scientific DXR) and rotational rheometer (Thermo Scientific HAAKE MARS III) are coupled through an optically transparent base modified from the Thermo Scientific RheoScope Module.

Rheology-Raman Spectroscopy: Tracking Polymer Crystallization with the

Combination of a Rheometer and a Raman-Microscope

Jan P. Plog1, Matthew Meyer2, Anthony Kotula3 and Kalman Migler3

1 Thermo Fisher Scientific, Karlsruhe, Germany

2 Thermo Fisher Scientific, Madison, USA 3 National Institute of Standards and Technology, Gaithersburg, USA

Simultaneous In-situ Analysis of Instabilities and First Normal StressDifference during Polymer Melt Extrusion Flows

Roland Kádár1,2, Ingo F. C. Naue2 and Manfred Wilhelm2

1 Chalmers University of Technology, 41258 Gothenburg, Sweden2 Karlsruhe Institute of Technology - KIT, 76128 Karlsruhe, Germany

ANNUAL TRANSACTIONS OF THE NORDIC RHEOLOGY SOCIETY, VOL. 24, 2016

ABSTRACTA high sensitivity system for capillaryrheometry capable of simultaneously de-tecting the onset and propagation of insta-bilities and the first normal stress differ-ence during polymer melt extrusion flowsis here presented. The main goals of thestudy are to analyse the nonlinear dynam-ics of extrusion instabilities and to deter-mine the first normal stress difference inthe presence of an induced streamline cur-vature via the so-called ’hole effect’. Anoverview of the system, general analysisprinciples, preliminary results and overallframework are herein discussed.

INTRODUCTIONCapillary rheometry is the preferredrheological characterisation method forpressure-driven processing applications,e.g. extrusion, injection moulding. Themain reason is that capillary rheometry isthe only method of probing material rheo-logical properties in processing-like condi-tions, i.e. high shear rate, nonlinear vis-coelastic regime, albeit in a controlledenvironment and using a comparativelysmall amount of material.1 Thus, it isof paramount importance to develop newtechniques to enhance capillary rheome-ters for a more comprehensive probing ofmaterial properties. Extrusion alone ac-counts for the processing of approximately35% of the worldwide production of plas-tics, currently 280⇥ 106 tons (Plastics Eu-rope, 2014). This makes it the most im-portant single polymer processing opera-

tion for the industry and can be found ina variety of forms in many manufacturingoperations. Extrusion throughput is lim-ited by the onset of instabilities, i.e. prod-uct defects. Comprehensive reviews on thesubject of polymer melt extrusion insta-bilities can be found elsewhere.4,6 A re-cent method proposed for the detectionand analysis of these instabilities is that ofa high sensitivity in-situ mechanical pres-sure instability detection system for cap-illary rheometry.8,10 The system consistsof high sensitivity piezoelectric transducersplaced along the extrusion slit die. In thisway all instability types detectable, thusopening new means of scientific inquiry. Asa result, new insights into the nonlinear dy-namics of the flow have been provided.9,14

Moreover, the possibility of investigatingthe reconstructed nonlinear dynamics wasconsidered, whereby a reconstructed phasespace is an embedding of the original phasespace.2,14 It was shown that a positive Lya-punov exponent was detected for the pri-mary and secondary instabilities in lin-ear and linear low density polyethylenes,LDPE and LLDPE,.14 Furthermore, it wasdetermined that Lyapunov exponents aresensitive to the changes in flow regime andbehave qualitatively different for the iden-tified transition sequences.14 It was alsoshown that it is possible to transfer thehigh sensitivity instability detection sys-tem to lab-sized extruders for inline ad-vanced processing control and quality con-trol systems.13

A very recent possibility considered

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