By application of optical coherence
tomography (OCT), an interferometric
noncontact imaging technique, the crystallization of a supercooled
poly(propylene) melt in a slit die is monitored. Both the quiescent
and the sheared melt are investigated, with a focus on experiments
where solidification and flow occur simultaneously. OCT is found to
be an excellent tool for that purpose since the resultant structures
are strongly scattering, which is a prerequisite for application of
that method. The resulting images enable for the first time to directly
monitor structure development throughout the whole experiment, including
final cooling to room temperature. By rendering the setup polarization-sensitive,
information on the birefringence of the pertinent structures is obtained.
The use of polarization-sensitive optical coherence tomography for monitoring the progress of a classical shear experiment in a slit die leads to new insights in the mechanisms of polymer crystallization. For the first time it is possible to get both depth and time resolved information on the development of different layers as a result of the processing conditions. By additionally measuring the transmitted light the method is at the same time fully compatible to conventional birefringence measurements. Microscopic analysis of the extruded stripes completes the description of the crystallization process.
We present a polarization-sensitive full-field optical coherence microscopy modality which is capable of simultaneously delivering depth resolved information on the reflectivity, optical retardation and optical axis orientation. In this way local birefringence, inherent stress–strain fields and optical anisotropies can be visualized with high resolution, as exemplified for various technical material applications.
We illustrate the abilities of an advanced full-field optical coherence microscope (FF-OCM) setup for characterization of technical materials with internal micro-structures and present this technique also for dynamic process monitoring, as strain-stress tests. Additionally we briefly illustrate the potential of image processing in context of the chosen applications. Furthermore, contrast modification techniques based on Fourier plane filtering are discussed.
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