Dresden 2011 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 40: Polymer Crystallization and Semicrystalline Polymers
CPP 40.7: Talk
Thursday, March 17, 2011, 12:15–12:30, ZEU 160
Application of Optical Coherence Tomography (OCT) for Monitoring the Crystallization of Polymers — •Peter Hierzenberger1, Gerhard Eder1, Elisabeth Leiss-Holzinger2, and David Stifter1 — 1Johannes Kepler University, Linz, Austria — 2Research Center for Non Destructive Testing GmbH, Linz, Austria
The use of Optical Coherence Tomography (OCT) as a novel non-destructive method for the investigation of structure development during polymer solidification is demonstrated. It is well known that the application of high shear gradients to crystallizable polymers produces highly oriented structures, whose development can be monitored by measuring the increasing optical retardation of the transmitted light. However, the increasing turbidity limits this method to conditions far from processing. By use of OCT - which measures reflected light in an interferometer arrangement - we are now able to go directly into that range and extend the experimental window to conditions more relevant to industrial polymer processing.
As a typical schedule molten isotactic poly(propylene) is extruded through a slit die, then quenched to a temperature slightly below the melting point, and after thermal equilibration sheared by resuming extrusion for a certain time. OCT enables on-line observation of structure development and gives depth-resolved images, which can be evaluated quantitatively afterwards and show the growth of the birefringent structures. Additionally, the cooled sample can be extracted and analyzed under the polarization microscope. Comparison of those ex-situ images with in-situ OCT images serves as validation of the method.